diff --git a/packages/core/src/js/feedback/FeedbackWidget.tsx b/packages/core/src/js/feedback/FeedbackWidget.tsx
index 7448d9d8b4..95b6e295fb 100644
--- a/packages/core/src/js/feedback/FeedbackWidget.tsx
+++ b/packages/core/src/js/feedback/FeedbackWidget.tsx
@@ -26,9 +26,7 @@ import { base64ToUint8Array, feedbackAlertDialog, isValidEmail  } from './utils'
  * Implements a feedback form screen that sends feedback to Sentry using Sentry.captureFeedback.
  */
 export class FeedbackWidget extends React.Component<FeedbackWidgetProps, FeedbackWidgetState> {
-  public static defaultProps: Partial<FeedbackWidgetProps> = {
-    ...defaultConfiguration
-  }
+  public static defaultProps = defaultConfiguration;
 
   private static _savedState: Omit<FeedbackWidgetState, 'isVisible'> = {
     name: '',
@@ -67,7 +65,7 @@ export class FeedbackWidget extends React.Component<FeedbackWidgetProps, Feedbac
   public handleFeedbackSubmit: () => void = () => {
     const { name, email, description } = this.state;
     const { onSubmitSuccess, onSubmitError, onFormSubmitted } = this.props;
-    const text: FeedbackTextConfiguration = this.props;
+    const text = this.props;
 
     const trimmedName = name?.trim();
     const trimmedEmail = email?.trim();
@@ -119,14 +117,14 @@ export class FeedbackWidget extends React.Component<FeedbackWidgetProps, Feedbac
 
   public onScreenshotButtonPress: () => void = async () => {
     if (!this.state.filename && !this.state.attachment) {
-      const imagePickerConfiguration: ImagePickerConfiguration = this.props;
-      if (imagePickerConfiguration.imagePicker) {
-        const launchImageLibrary = imagePickerConfiguration.imagePicker.launchImageLibraryAsync
+      const { imagePicker } = this.props;
+      if (imagePicker) {
+        const launchImageLibrary = imagePicker.launchImageLibraryAsync
           // expo-image-picker library is available
-          ? () => imagePickerConfiguration.imagePicker.launchImageLibraryAsync({ mediaTypes: ['images'], base64: isWeb() })
+          ? () => imagePicker.launchImageLibraryAsync?.({ mediaTypes: ['images'], base64: isWeb() })
           // react-native-image-picker library is available
-          : imagePickerConfiguration.imagePicker.launchImageLibrary
-            ? () => imagePickerConfiguration.imagePicker.launchImageLibrary({ mediaType: 'photo', includeBase64: isWeb() })
+          : imagePicker.launchImageLibrary
+            ? () => imagePicker.launchImageLibrary?.({ mediaType: 'photo', includeBase64: isWeb() })
             : null;
         if (!launchImageLibrary) {
           logger.warn('No compatible image picker library found. Please provide a valid image picker library.');
@@ -140,22 +138,22 @@ export class FeedbackWidget extends React.Component<FeedbackWidgetProps, Feedbac
         }
 
         const result = await launchImageLibrary();
-        if (result.assets && result.assets.length > 0) {
+        if (result?.assets && result.assets.length > 0) {
           if (isWeb()) {
-            const filename = result.assets[0].fileName;
-            const imageUri = result.assets[0].uri;
-            const base64 = result.assets[0].base64;
-            const data = base64ToUint8Array(base64);
-            if (data != null) {
+            const filename = result.assets[0]?.fileName;
+            const imageUri = result.assets[0]?.uri;
+            const base64 = result.assets[0]?.base64;
+            const data = base64 ? base64ToUint8Array(base64) : undefined;
+            if (data) {
               this.setState({ filename, attachment: data, attachmentUri: imageUri });
             } else {
               logger.error('Failed to read image data on the web');
             }
           } else {
-            const filename = result.assets[0].fileName;
-            const imageUri = result.assets[0].uri;
-            getDataFromUri(imageUri).then((data) => {
-              if (data != null) {
+            const filename = result.assets[0]?.fileName;
+            const imageUri = result.assets[0]?.uri;
+            imageUri && getDataFromUri(imageUri).then((data) => {
+              if (data) {
                 this.setState({ filename, attachment: data, attachmentUri: imageUri });
               } else {
                 logger.error('Failed to read image data from uri:', imageUri);
diff --git a/packages/core/src/js/feedback/FeedbackWidget.types.ts b/packages/core/src/js/feedback/FeedbackWidget.types.ts
index af08c2ffc3..adb300784b 100644
--- a/packages/core/src/js/feedback/FeedbackWidget.types.ts
+++ b/packages/core/src/js/feedback/FeedbackWidget.types.ts
@@ -21,38 +21,38 @@ export interface FeedbackGeneralConfiguration {
    *
    * @default true
    */
-  showBranding?: boolean;
+  showBranding: boolean;
 
   /**
    * Should the email field be required?
    */
-  isEmailRequired?: boolean;
+  isEmailRequired: boolean;
 
   /**
    * Should the email field be validated?
    */
-  shouldValidateEmail?: boolean;
+  shouldValidateEmail: boolean;
 
   /**
    * Should the name field be required?
    */
-  isNameRequired?: boolean;
+  isNameRequired: boolean;
 
   /**
    * Should the email input field be visible? Note: email will still be collected if set via `Sentry.setUser()`
    */
-  showEmail?: boolean;
+  showEmail: boolean;
 
   /**
    * Should the name input field be visible? Note: name will still be collected if set via `Sentry.setUser()`
    */
-  showName?: boolean;
+  showName: boolean;
 
   /**
    * This flag determines whether the "Add Screenshot" button is displayed
    * @default false
    */
-  enableScreenshot?: boolean;
+  enableScreenshot: boolean;
 
   /**
    * Fill in email/name input fields with Sentry user context if it exists.
@@ -71,32 +71,32 @@ export interface FeedbackTextConfiguration {
   /**
    * The label for the Feedback form cancel button that closes dialog
    */
-  cancelButtonLabel?: string;
+  cancelButtonLabel: string;
 
   /**
    * The label for the Feedback form submit button that sends feedback
    */
-  submitButtonLabel?: string;
+  submitButtonLabel: string;
 
   /**
    * The title of the Feedback form
    */
-  formTitle?: string;
+  formTitle: string;
 
   /**
    * Label for the email input
    */
-  emailLabel?: string;
+  emailLabel: string;
 
   /**
    * Placeholder text for Feedback email input
    */
-  emailPlaceholder?: string;
+  emailPlaceholder: string;
 
   /**
    * Label for the message input
    */
-  messageLabel?: string;
+  messageLabel: string;
 
   /**
    * Placeholder text for Feedback message input
@@ -106,52 +106,52 @@ export interface FeedbackTextConfiguration {
   /**
    * Label for the name input
    */
-  nameLabel?: string;
+  nameLabel: string;
 
   /**
    * Message after feedback was sent successfully
    */
-  successMessageText?: string;
+  successMessageText: string;
 
   /**
    * Placeholder text for Feedback name input
    */
-  namePlaceholder?: string;
+  namePlaceholder: string;
 
   /**
    * Text which indicates that a field is required
    */
-  isRequiredLabel?: string;
+  isRequiredLabel: string;
 
   /**
    * The label for the button that adds a screenshot and renders the image editor
    */
-  addScreenshotButtonLabel?: string;
+  addScreenshotButtonLabel: string;
 
   /**
    * The label for the button that removes a screenshot and hides the image editor
    */
-  removeScreenshotButtonLabel?: string;
+  removeScreenshotButtonLabel: string;
 
   /**
    * The title of the error dialog
    */
-  errorTitle?: string;
+  errorTitle: string;
 
   /**
    * The error message when the form is invalid
    */
-  formError?: string;
+  formError: string;
 
   /**
    * The error message when the email is invalid
    */
-  emailError?: string;
+  emailError: string;
 
   /**
    * Message when there is a generic error
    */
-  genericError?: string;
+  genericError: string;
 }
 
 /**
@@ -161,34 +161,34 @@ export interface FeedbackCallbacks {
   /**
    * Callback when form is opened
    */
-  onFormOpen?: () => void;
+  onFormOpen: () => void;
 
   /**
    * Callback when form is closed and not submitted
    */
-  onFormClose?: () => void;
+  onFormClose: () => void;
 
   /**
    * Callback when a screenshot is added
    */
-  onAddScreenshot?: (addScreenshot: (uri: string) => void) => void;
+  onAddScreenshot: (addScreenshot: (uri: string) => void) => void;
 
   /**
    * Callback when feedback is successfully submitted
    *
    * After this you'll see a SuccessMessage on the screen for a moment.
    */
-  onSubmitSuccess?: (data: FeedbackFormData) => void;
+  onSubmitSuccess: (data: FeedbackFormData) => void;
 
   /**
    * Callback when feedback is unsuccessfully submitted
    */
-  onSubmitError?: (error: Error) => void;
+  onSubmitError: (error: Error) => void;
 
   /**
    * Callback when the feedback form is submitted successfully, and the SuccessMessage is complete, or dismissed
    */
-  onFormSubmitted?: () => void;
+  onFormSubmitted: () => void;
 }
 
 /**
diff --git a/packages/core/src/js/feedback/FeedbackWidgetManager.tsx b/packages/core/src/js/feedback/FeedbackWidgetManager.tsx
index 856298382e..4f380842e3 100644
--- a/packages/core/src/js/feedback/FeedbackWidgetManager.tsx
+++ b/packages/core/src/js/feedback/FeedbackWidgetManager.tsx
@@ -15,6 +15,10 @@ const PULL_DOWN_CLOSE_THRESHOLD = 200;
 const SLIDE_ANIMATION_DURATION = 200;
 const BACKGROUND_ANIMATION_DURATION = 200;
 
+const NOOP_SET_VISIBILITY = (): void => {
+  // No-op
+};
+
 class FeedbackWidgetManager {
   private static _isVisible = false;
   private static _setVisibility: (visible: boolean) => void;
@@ -28,22 +32,24 @@ class FeedbackWidgetManager {
    */
   public static reset(): void {
     this._isVisible = false;
-    this._setVisibility = undefined;
+    this._setVisibility = NOOP_SET_VISIBILITY;
   }
 
   public static show(): void {
-    if (this._setVisibility) {
+    if (this._setVisibility !== NOOP_SET_VISIBILITY) {
       this._isVisible = true;
       this._setVisibility(true);
     } else {
       // This message should be always shown otherwise it's not possible to use the widget.
       // eslint-disable-next-line no-console
-      console.warn('[Sentry] FeedbackWidget requires `Sentry.wrap(RootComponent)` to be called before `showFeedbackWidget()`.');
+      console.warn(
+        '[Sentry] FeedbackWidget requires `Sentry.wrap(RootComponent)` to be called before `showFeedbackWidget()`.',
+      );
     }
   }
 
   public static hide(): void {
-    if (this._setVisibility) {
+    if (this._setVisibility !== NOOP_SET_VISIBILITY) {
       this._isVisible = false;
       this._setVisibility(false);
     } else {
diff --git a/packages/core/src/js/feedback/defaults.ts b/packages/core/src/js/feedback/defaults.ts
index 90d9534874..3152c769fb 100644
--- a/packages/core/src/js/feedback/defaults.ts
+++ b/packages/core/src/js/feedback/defaults.ts
@@ -19,7 +19,7 @@ const ADD_SCREENSHOT_LABEL = 'Add a screenshot';
 const REMOVE_SCREENSHOT_LABEL = 'Remove screenshot';
 const GENERIC_ERROR_TEXT = 'Unable to send feedback due to an unexpected error.';
 
-export const defaultConfiguration: Partial<FeedbackWidgetProps> = {
+export const defaultConfiguration: FeedbackWidgetProps = {
   // FeedbackCallbacks
   onFormOpen: () => {
     // Does nothing by default
diff --git a/packages/core/src/js/feedback/integration.ts b/packages/core/src/js/feedback/integration.ts
index 96280cf967..ad2bd0675b 100644
--- a/packages/core/src/js/feedback/integration.ts
+++ b/packages/core/src/js/feedback/integration.ts
@@ -8,7 +8,7 @@ type FeedbackIntegration = Integration & {
   options: Partial<FeedbackWidgetProps>;
 };
 
-export const feedbackIntegration = (initOptions: FeedbackWidgetProps = {}): FeedbackIntegration => {
+export const feedbackIntegration = (initOptions: Partial<FeedbackWidgetProps> = {}): FeedbackIntegration => {
   return {
     name: MOBILE_FEEDBACK_INTEGRATION_NAME,
     options: initOptions,
diff --git a/packages/core/src/js/feedback/utils.ts b/packages/core/src/js/feedback/utils.ts
index 9c2826981d..05b8b471f1 100644
--- a/packages/core/src/js/feedback/utils.ts
+++ b/packages/core/src/js/feedback/utils.ts
@@ -15,7 +15,7 @@ declare global {
  */
 export function isModalSupported(): boolean {
   const { major, minor } = ReactNativeLibraries.ReactNativeVersion?.version || {};
-  return !(isFabricEnabled() && major === 0 && minor < 71);
+  return !(isFabricEnabled() && major === 0 && minor && minor < 71);
 }
 
 export const isValidEmail = (email: string): boolean => {
diff --git a/packages/core/src/js/integrations/debugsymbolicator.ts b/packages/core/src/js/integrations/debugsymbolicator.ts
index 3ff5bc5169..ed1c2901d3 100644
--- a/packages/core/src/js/integrations/debugsymbolicator.ts
+++ b/packages/core/src/js/integrations/debugsymbolicator.ts
@@ -131,7 +131,7 @@ async function convertReactNativeFramesToSentryFrames(frames: ReactNative.StackF
  * @param event Event
  * @param frames StackFrame[]
  */
-function replaceExceptionFramesInException(exception: Exception, frames: SentryStackFrame[]): void {
+function replaceExceptionFramesInException(exception: Exception | undefined, frames: SentryStackFrame[]): void {
   if (exception?.stacktrace) {
     exception.stacktrace.frames = frames.reverse();
   }
diff --git a/packages/core/src/js/integrations/debugsymbolicatorutils.ts b/packages/core/src/js/integrations/debugsymbolicatorutils.ts
index 2b51171b39..d99f72b261 100644
--- a/packages/core/src/js/integrations/debugsymbolicatorutils.ts
+++ b/packages/core/src/js/integrations/debugsymbolicatorutils.ts
@@ -20,7 +20,14 @@ export async function fetchSourceContext(frames: SentryStackFrame[]): Promise<Se
         return;
       }
 
-      xhr.open('POST', getSentryMetroSourceContextUrl(), true);
+      const url = getSentryMetroSourceContextUrl();
+      if (!url) {
+        logger.error('Could not fetch source context. No dev server URL found.');
+        resolve(frames);
+        return;
+      }
+
+      xhr.open('POST', url, true);
       xhr.setRequestHeader('Content-Type', 'application/json');
       xhr.send(JSON.stringify({ stack: frames }));
 
@@ -52,8 +59,14 @@ export async function fetchSourceContext(frames: SentryStackFrame[]): Promise<Se
   });
 }
 
-function getSentryMetroSourceContextUrl(): string {
-  return `${getDevServer().url}__sentry/context`;
+function getSentryMetroSourceContextUrl(): string | undefined {
+  const devServer = getDevServer();
+
+  if (!devServer) {
+    return undefined;
+  }
+
+  return `${devServer.url}__sentry/context`;
 }
 
 /**
diff --git a/packages/core/src/js/integrations/default.ts b/packages/core/src/js/integrations/default.ts
index 024e1fb325..e6cf250af7 100644
--- a/packages/core/src/js/integrations/default.ts
+++ b/packages/core/src/js/integrations/default.ts
@@ -142,8 +142,8 @@ export function getDefaultIntegrations(options: ReactNativeClientOptions): Integ
 
   if (!hasReplayOptions && hasExperimentsReplayOptions) {
     // Remove in the next major version (v7)
-    options.replaysOnErrorSampleRate = options._experiments.replaysOnErrorSampleRate;
-    options.replaysSessionSampleRate = options._experiments.replaysSessionSampleRate;
+    options.replaysOnErrorSampleRate = options._experiments?.replaysOnErrorSampleRate;
+    options.replaysSessionSampleRate = options._experiments?.replaysSessionSampleRate;
   }
 
   if ((hasReplayOptions || hasExperimentsReplayOptions) && notWeb()) {
diff --git a/packages/core/src/js/integrations/screenshot.ts b/packages/core/src/js/integrations/screenshot.ts
index 84bb72c2b4..11491689ee 100644
--- a/packages/core/src/js/integrations/screenshot.ts
+++ b/packages/core/src/js/integrations/screenshot.ts
@@ -18,13 +18,13 @@ export const screenshotIntegration = (): Integration => {
 };
 
 async function processEvent(event: Event, hint: EventHint, client: ReactNativeClient): Promise<Event> {
-  const hasException = event.exception?.values?.length > 0;
+  const hasException = event.exception?.values && event.exception.values.length > 0;
   if (!hasException || client.getOptions().beforeScreenshot?.(event, hint) === false) {
     return event;
   }
 
   const screenshots: ScreenshotAttachment[] | null = await NATIVE.captureScreenshot();
-  if (screenshots?.length > 0) {
+  if (screenshots && screenshots.length > 0) {
     hint.attachments = [...screenshots, ...(hint?.attachments || [])];
   }
 
diff --git a/packages/core/src/js/integrations/spotlight.ts b/packages/core/src/js/integrations/spotlight.ts
index 50191aa132..90af07ccca 100644
--- a/packages/core/src/js/integrations/spotlight.ts
+++ b/packages/core/src/js/integrations/spotlight.ts
@@ -83,17 +83,23 @@ function sendEnvelopesToSidecar(client: Client, sidecarUrl: string): void {
   });
 }
 
+const DEFAULT_SIDECAR_URL = 'http://localhost:8969/stream';
+
 /**
  * Gets the default Spotlight sidecar URL.
  */
 export function getDefaultSidecarUrl(): string {
   try {
-    const { url } = ReactNativeLibraries.Devtools?.getDevServer();
+    const { url } = ReactNativeLibraries.Devtools?.getDevServer() ?? {};
+    if (!url) {
+      return DEFAULT_SIDECAR_URL;
+    }
+
     return `http://${getHostnameFromString(url)}:8969/stream`;
   } catch (_oO) {
     // We can't load devserver URL
   }
-  return 'http://localhost:8969/stream';
+  return DEFAULT_SIDECAR_URL;
 }
 
 /**
diff --git a/packages/core/src/js/integrations/viewhierarchy.ts b/packages/core/src/js/integrations/viewhierarchy.ts
index d4d4530b15..c2c56fa4fc 100644
--- a/packages/core/src/js/integrations/viewhierarchy.ts
+++ b/packages/core/src/js/integrations/viewhierarchy.ts
@@ -21,7 +21,7 @@ export const viewHierarchyIntegration = (): Integration => {
 };
 
 async function processEvent(event: Event, hint: EventHint): Promise<Event> {
-  const hasException = event.exception?.values?.length > 0;
+  const hasException = event.exception?.values && event.exception.values.length > 0;
   if (!hasException) {
     return event;
   }
diff --git a/packages/core/src/js/profiling/convertHermesProfile.ts b/packages/core/src/js/profiling/convertHermesProfile.ts
index 6db66dd6d5..241c6fd249 100644
--- a/packages/core/src/js/profiling/convertHermesProfile.ts
+++ b/packages/core/src/js/profiling/convertHermesProfile.ts
@@ -82,11 +82,21 @@ export function mapSamples(
   hermesStacks: Set<Hermes.StackFrameId>;
   jsThreads: Set<ThreadId>;
 } {
+  const samples: ThreadCpuSample[] = [];
   const jsThreads = new Set<ThreadId>();
   const hermesStacks = new Set<Hermes.StackFrameId>();
 
-  const start = Number(hermesSamples[0].ts);
-  const samples: ThreadCpuSample[] = [];
+  const firstSample = hermesSamples[0];
+  if (!firstSample) {
+    logger.warn('[Profiling] No samples found in profile.');
+    return {
+      samples,
+      hermesStacks,
+      jsThreads,
+    };
+  }
+
+  const start = Number(firstSample.ts);
   for (const hermesSample of hermesSamples) {
     jsThreads.add(hermesSample.tid);
     hermesStacks.add(hermesSample.sf);
@@ -130,8 +140,12 @@ function mapFrames(hermesStackFrames: Record<Hermes.StackFrameId, Hermes.StackFr
     if (!Object.prototype.hasOwnProperty.call(hermesStackFrames, key)) {
       continue;
     }
-    hermesStackFrameIdToSentryFrameIdMap.set(Number(key), frames.length);
-    frames.push(parseHermesJSStackFrame(hermesStackFrames[key]));
+
+    const hermesStackFrame = hermesStackFrames[key];
+    if (hermesStackFrame) {
+      hermesStackFrameIdToSentryFrameIdMap.set(Number(key), frames.length);
+      frames.push(parseHermesJSStackFrame(hermesStackFrame));
+    }
   }
 
   return {
diff --git a/packages/core/src/js/profiling/debugid.ts b/packages/core/src/js/profiling/debugid.ts
index f5843eb2bc..ae05814b15 100644
--- a/packages/core/src/js/profiling/debugid.ts
+++ b/packages/core/src/js/profiling/debugid.ts
@@ -25,12 +25,22 @@ export function getDebugMetadata(): DebugImage[] {
     logger.warn(
       '[Profiling] Multiple debug images found, but only one one bundle is supported. Using the first one...',
     );
+    return [];
+  }
+
+  if (!debugIdsKeys[0]) {
+    return [];
+  }
+
+  const debugId = debugIdMap[debugIdsKeys[0]];
+  if (!debugId) {
+    return [];
   }
 
   return [
     {
       code_file: DEFAULT_BUNDLE_NAME,
-      debug_id: debugIdMap[debugIdsKeys[0]],
+      debug_id: debugId,
       type: 'sourcemap',
     },
   ];
diff --git a/packages/core/src/js/replay/mobilereplay.ts b/packages/core/src/js/replay/mobilereplay.ts
index d0db1810f4..3b63e40957 100644
--- a/packages/core/src/js/replay/mobilereplay.ts
+++ b/packages/core/src/js/replay/mobilereplay.ts
@@ -103,7 +103,7 @@ export const mobileReplayIntegration = (initOptions: MobileReplayOptions = defau
   const options = { ...defaultOptions, ...initOptions };
 
   async function processEvent(event: Event): Promise<Event> {
-    const hasException = event.exception?.values?.length > 0;
+    const hasException = event.exception?.values && event.exception.values.length > 0;
     if (!hasException) {
       // Event is not an error, will not capture replay
       return event;
diff --git a/packages/core/src/js/scopeSync.ts b/packages/core/src/js/scopeSync.ts
index bc9f20c597..bc69ffe86d 100644
--- a/packages/core/src/js/scopeSync.ts
+++ b/packages/core/src/js/scopeSync.ts
@@ -1,4 +1,5 @@
 import type { Breadcrumb, Scope } from '@sentry/core';
+import { logger } from '@sentry/react';
 
 import { DEFAULT_BREADCRUMB_LEVEL } from './breadcrumb';
 import { fillTyped } from './utils/fill';
@@ -60,7 +61,11 @@ export function enableSyncToNative(scope: Scope): void {
     original.call(scope, mergedBreadcrumb, maxBreadcrumbs);
 
     const finalBreadcrumb = scope.getLastBreadcrumb();
-    NATIVE.addBreadcrumb(finalBreadcrumb);
+    if (finalBreadcrumb) {
+      NATIVE.addBreadcrumb(finalBreadcrumb);
+    } else {
+      logger.warn('[ScopeSync] Last created breadcrumb is undefined. Skipping sync to native.');
+    }
 
     return scope;
   });
diff --git a/packages/core/src/js/sdk.tsx b/packages/core/src/js/sdk.tsx
index dd6a176322..c50f1c35f1 100644
--- a/packages/core/src/js/sdk.tsx
+++ b/packages/core/src/js/sdk.tsx
@@ -63,7 +63,7 @@ export function init(passedOptions: ReactNativeOptions): void {
     enableSyncToNative(getIsolationScope());
   }
 
-  const getURLFromDSN = (dsn: string | null): string | undefined => {
+  const getURLFromDSN = (dsn: string | undefined): string | undefined => {
     if (!dsn) {
       return undefined;
     }
diff --git a/packages/core/src/js/touchevents.tsx b/packages/core/src/js/touchevents.tsx
index 293391a834..2280597264 100644
--- a/packages/core/src/js/touchevents.tsx
+++ b/packages/core/src/js/touchevents.tsx
@@ -121,8 +121,12 @@ class TouchEventBoundary extends React.Component<TouchEventBoundaryProps> {
     const level = 'info' as SeverityLevel;
 
     const root = touchPath[0];
-    const detail = label ? label : `${root.name}${root.file ? ` (${root.file})` : ''}`;
+    if (!root) {
+      logger.warn('[TouchEvents] No root component found in touch path.');
+      return;
+    }
 
+    const detail = label ? label : `${root.name}${root.file ? ` (${root.file})` : ''}`;
     const crumb = {
       category: this.props.breadcrumbCategory,
       data: { path: touchPath },
diff --git a/packages/core/src/js/tracing/integrations/appStart.ts b/packages/core/src/js/tracing/integrations/appStart.ts
index acd5096bc4..aa2ce1c70e 100644
--- a/packages/core/src/js/tracing/integrations/appStart.ts
+++ b/packages/core/src/js/tracing/integrations/appStart.ts
@@ -211,6 +211,13 @@ export const appStartIntegration = ({
   };
 
   async function captureStandaloneAppStart(): Promise<void> {
+    if (!_client) {
+      // If client is not set, SDK was not initialized, logger is thus disabled
+      // eslint-disable-next-line no-console
+      console.warn('[AppStart] Could not capture App Start, missing client, call `Sentry.init` first.');
+      return;
+    }
+
     if (!standalone) {
       logger.debug(
         '[AppStart] App start tracking is enabled. App start will be added to the first transaction as a child span.',
diff --git a/packages/core/src/js/tracing/integrations/nativeFrames.ts b/packages/core/src/js/tracing/integrations/nativeFrames.ts
index ceec914b88..e5dd20f98a 100644
--- a/packages/core/src/js/tracing/integrations/nativeFrames.ts
+++ b/packages/core/src/js/tracing/integrations/nativeFrames.ts
@@ -60,7 +60,7 @@ export const createNativeFramesIntegrations = (enable: boolean | undefined): Int
 export const nativeFramesIntegration = (): Integration => {
   /** The native frames at the finish time of the most recent span. */
   let _lastChildSpanEndFrames: NativeFramesResponseWithTimestamp | null = null;
-  const _spanToNativeFramesAtStartMap: AsyncExpiringMap<string, NativeFramesResponse> = new AsyncExpiringMap({
+  const _spanToNativeFramesAtStartMap: AsyncExpiringMap<string, NativeFramesResponse | null> = new AsyncExpiringMap({
     ttl: START_FRAMES_TIMEOUT_MS,
   });
   const _spanToNativeFramesAtEndMap: AsyncExpiringMap<string, NativeFramesResponseWithTimestamp | null> =
diff --git a/packages/core/src/js/tracing/integrations/timeToDisplayIntegration.ts b/packages/core/src/js/tracing/integrations/timeToDisplayIntegration.ts
index 6f48b4b877..8b5d0ffc66 100644
--- a/packages/core/src/js/tracing/integrations/timeToDisplayIntegration.ts
+++ b/packages/core/src/js/tracing/integrations/timeToDisplayIntegration.ts
@@ -30,7 +30,7 @@ export const timeToDisplayIntegration = (): Integration => {
         return event;
       }
 
-      const rootSpanId = event.contexts.trace.span_id;
+      const rootSpanId = event.contexts?.trace?.span_id;
       if (!rootSpanId) {
         logger.warn(`[${INTEGRATION_NAME}] No root span id found in transaction.`);
         return event;
@@ -64,7 +64,9 @@ export const timeToDisplayIntegration = (): Integration => {
       if (ttfdSpan?.start_timestamp && ttfdSpan?.timestamp) {
         const durationMs = (ttfdSpan.timestamp - ttfdSpan.start_timestamp) * 1000;
         if (isDeadlineExceeded(durationMs)) {
-          event.measurements['time_to_full_display'] = event.measurements['time_to_initial_display'];
+          if (event.measurements['time_to_initial_display']) {
+            event.measurements['time_to_full_display'] = event.measurements['time_to_initial_display'];
+          }
         } else {
           event.measurements['time_to_full_display'] = {
             value: durationMs,
@@ -100,6 +102,8 @@ async function addTimeToInitialDisplay({
 }): Promise<SpanJSON | undefined> {
   const ttidEndTimestampSeconds = await NATIVE.popTimeToDisplayFor(`ttid-${rootSpanId}`);
 
+  event.spans = event.spans || [];
+
   let ttidSpan: SpanJSON | undefined = event.spans?.find(span => span.op === UI_LOAD_INITIAL_DISPLAY);
 
   if (ttidSpan && (ttidSpan.status === undefined || ttidSpan.status === 'ok') && !ttidEndTimestampSeconds) {
@@ -204,11 +208,13 @@ async function addTimeToFullDisplay({
     return undefined;
   }
 
+  event.spans = event.spans || [];
+
   let ttfdSpan = event.spans?.find(span => span.op === UI_LOAD_FULL_DISPLAY);
 
   let ttfdAdjustedEndTimestampSeconds = ttfdEndTimestampSeconds;
-  const ttfdIsBeforeTtid = ttidSpan?.timestamp && ttfdEndTimestampSeconds < ttidSpan.timestamp;
-  if (ttfdIsBeforeTtid) {
+  const ttfdIsBeforeTtid = ttidSpan.timestamp && ttfdEndTimestampSeconds < ttidSpan.timestamp;
+  if (ttfdIsBeforeTtid && ttidSpan.timestamp) {
     ttfdAdjustedEndTimestampSeconds = ttidSpan.timestamp;
   }
 
diff --git a/packages/core/src/js/tracing/onSpanEndUtils.ts b/packages/core/src/js/tracing/onSpanEndUtils.ts
index 4ae3c027f6..cffa13a852 100644
--- a/packages/core/src/js/tracing/onSpanEndUtils.ts
+++ b/packages/core/src/js/tracing/onSpanEndUtils.ts
@@ -44,7 +44,7 @@ export const adjustTransactionDuration = (client: Client, span: Span, maxDuratio
   });
 };
 
-export const ignoreEmptyBackNavigation = (client: Client | undefined, span: Span): void => {
+export const ignoreEmptyBackNavigation = (client: Client | undefined, span: Span | undefined): void => {
   if (!client) {
     logger.warn('Could not hook on spanEnd event because client is not defined.');
     return;
diff --git a/packages/core/src/js/tracing/reactnavigation.ts b/packages/core/src/js/tracing/reactnavigation.ts
index 8528466d11..feebb3b9f7 100644
--- a/packages/core/src/js/tracing/reactnavigation.ts
+++ b/packages/core/src/js/tracing/reactnavigation.ts
@@ -220,6 +220,7 @@ export const reactNavigationIntegration = ({
     const navigationActionType = useDispatchedActionData ? event?.data.action.type : undefined;
     if (
       useDispatchedActionData &&
+      navigationActionType &&
       [
         // Process common actions
         'PRELOAD',
@@ -252,12 +253,12 @@ export const reactNavigationIntegration = ({
       ignoreEmptyBackNavigation(getClient(), latestNavigationSpan);
     }
 
-    if (enableTimeToInitialDisplay) {
-      NATIVE.setActiveSpanId(latestNavigationSpan?.spanContext().spanId);
+    if (enableTimeToInitialDisplay && latestNavigationSpan) {
+      NATIVE.setActiveSpanId(latestNavigationSpan.spanContext().spanId);
       navigationProcessingSpan = startInactiveSpan({
         op: 'navigation.processing',
         name: 'Navigation dispatch to navigation cancelled or screen mounted',
-        startTime: latestNavigationSpan && spanToJSON(latestNavigationSpan).start_timestamp,
+        startTime: spanToJSON(latestNavigationSpan).start_timestamp,
       });
       navigationProcessingSpan.setAttribute(
         SEMANTIC_ATTRIBUTE_SENTRY_ORIGIN,
diff --git a/packages/core/src/js/tracing/span.ts b/packages/core/src/js/tracing/span.ts
index c4b89b8d74..4e3a70ff66 100644
--- a/packages/core/src/js/tracing/span.ts
+++ b/packages/core/src/js/tracing/span.ts
@@ -127,7 +127,7 @@ export function getDefaultIdleNavigationSpanOptions(): StartSpanOptions {
  * Checks if the span is a Sentry User Interaction span.
  */
 export function isSentryInteractionSpan(span: Span): boolean {
-  return [SPAN_ORIGIN_AUTO_INTERACTION, SPAN_ORIGIN_MANUAL_INTERACTION].includes(spanToJSON(span).origin);
+  return [SPAN_ORIGIN_AUTO_INTERACTION, SPAN_ORIGIN_MANUAL_INTERACTION].includes(spanToJSON(span).origin || '');
 }
 
 export const SCOPE_SPAN_FIELD = '_sentrySpan';
diff --git a/packages/core/src/js/tracing/timeToDisplayFallback.ts b/packages/core/src/js/tracing/timeToDisplayFallback.ts
index cd71b21df0..e854d43477 100644
--- a/packages/core/src/js/tracing/timeToDisplayFallback.ts
+++ b/packages/core/src/js/tracing/timeToDisplayFallback.ts
@@ -13,6 +13,6 @@ export const addTimeToInitialDisplayFallback = (
   spanIdToTimeToInitialDisplayFallback.set(spanId, timestampSeconds);
 };
 
-export const getTimeToInitialDisplayFallback = async (spanId: string): Promise<number | undefined> => {
+export const getTimeToInitialDisplayFallback = async (spanId: string): Promise<number | undefined | null> => {
   return spanIdToTimeToInitialDisplayFallback.get(spanId);
 };
diff --git a/packages/core/src/js/transports/encodePolyfill.ts b/packages/core/src/js/transports/encodePolyfill.ts
index 102d1886fb..e9244d562a 100644
--- a/packages/core/src/js/transports/encodePolyfill.ts
+++ b/packages/core/src/js/transports/encodePolyfill.ts
@@ -1,16 +1,12 @@
 import { getMainCarrier, SDK_VERSION } from '@sentry/core';
 
-import type { RN_GLOBAL_OBJ } from '../utils/worldwide';
 import { utf8ToBytes } from '../vendor';
 
 export const useEncodePolyfill = (): void => {
-  const globalCarriers = getMainCarrier().__SENTRY__;
-
-  if (!globalCarriers) {
-    (globalCarriers as Partial<(typeof RN_GLOBAL_OBJ)['__SENTRY__']>) = {};
-  }
-
-  globalCarriers[SDK_VERSION].encodePolyfill = encodePolyfill;
+  // Based on https://github.com/getsentry/sentry-javascript/blob/f0fc41f6166857cd97a695f5cc9a18caf6a0bf43/packages/core/src/carrier.ts#L49
+  const carrier = getMainCarrier();
+  const __SENTRY__ = (carrier.__SENTRY__ = carrier.__SENTRY__ || {});
+  (__SENTRY__[SDK_VERSION] = __SENTRY__[SDK_VERSION] || {}).encodePolyfill = encodePolyfill;
 };
 
 export const encodePolyfill = (text: string): Uint8Array => {
diff --git a/packages/core/src/js/utils/AsyncExpiringMap.ts b/packages/core/src/js/utils/AsyncExpiringMap.ts
index 657286ed26..bba14e01f1 100644
--- a/packages/core/src/js/utils/AsyncExpiringMap.ts
+++ b/packages/core/src/js/utils/AsyncExpiringMap.ts
@@ -7,7 +7,7 @@ export class AsyncExpiringMap<K, V> {
   private _ttl: number;
   private _cleanupIntervalMs: number;
   private _map: Map<K, { value: V | undefined; expiresAt: number | null; promise: PromiseLike<V> | null }>;
-  private _cleanupInterval: ReturnType<typeof setInterval>;
+  private _cleanupInterval: ReturnType<typeof setInterval> | undefined;
 
   public constructor({
     cleanupInterval = 5_000,
@@ -30,7 +30,7 @@ export class AsyncExpiringMap<K, V> {
       this.startCleanup();
     }
 
-    if (typeof promise !== 'object' || !('then' in promise)) {
+    if (typeof promise !== 'object' || !promise || !('then' in promise)) {
       this._map.set(key, { value: promise, expiresAt: Date.now() + this._ttl, promise: null });
       return;
     }
@@ -143,7 +143,9 @@ export class AsyncExpiringMap<K, V> {
    * Clear all entries.
    */
   public clear(): void {
-    clearInterval(this._cleanupInterval);
+    if (this._cleanupInterval) {
+      clearInterval(this._cleanupInterval);
+    }
     this._map.clear();
   }
 
@@ -151,7 +153,9 @@ export class AsyncExpiringMap<K, V> {
    * Stop the cleanup interval.
    */
   public stopCleanup(): void {
-    clearInterval(this._cleanupInterval);
+    if (this._cleanupInterval) {
+      clearInterval(this._cleanupInterval);
+    }
   }
 
   /**
diff --git a/packages/core/src/js/vendor/base64-js/fromByteArray.ts b/packages/core/src/js/vendor/base64-js/fromByteArray.ts
index 51c046b0a4..11c771f1d5 100644
--- a/packages/core/src/js/vendor/base64-js/fromByteArray.ts
+++ b/packages/core/src/js/vendor/base64-js/fromByteArray.ts
@@ -28,10 +28,12 @@ const lookup: string[] = [];
 
 const code = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
 for (let i = 0, len = code.length; i < len; ++i) {
+  // @ts-expect-error
   lookup[i] = code[i];
 }
 
 function tripletToBase64(num: number): string {
+  // @ts-expect-error
   return lookup[(num >> 18) & 0x3f] + lookup[(num >> 12) & 0x3f] + lookup[(num >> 6) & 0x3f] + lookup[num & 0x3f];
 }
 
@@ -39,6 +41,7 @@ function encodeChunk(uint8: Uint8Array | number[], start: number, end: number):
   let tmp;
   const output = [];
   for (let i = start; i < end; i += 3) {
+    // @ts-expect-error
     tmp = ((uint8[i] << 16) & 0xff0000) + ((uint8[i + 1] << 8) & 0xff00) + (uint8[i + 2] & 0xff);
     output.push(tripletToBase64(tmp));
   }
@@ -63,9 +66,12 @@ export function base64StringFromByteArray(uint8: Uint8Array | number[]): string
   // pad the end with zeros, but make sure to not forget the extra bytes
   if (extraBytes === 1) {
     tmp = uint8[len - 1];
+    // @ts-expect-error
     parts.push(`${lookup[tmp >> 2] + lookup[(tmp << 4) & 0x3f]}==`);
   } else if (extraBytes === 2) {
+    // @ts-expect-error
     tmp = (uint8[len - 2] << 8) + uint8[len - 1];
+    // @ts-expect-error
     parts.push(`${lookup[tmp >> 10] + lookup[(tmp >> 4) & 0x3f] + lookup[(tmp << 2) & 0x3f]}=`);
   }
 
diff --git a/packages/core/src/js/wrapper.ts b/packages/core/src/js/wrapper.ts
index 31152c02b2..289af29923 100644
--- a/packages/core/src/js/wrapper.ts
+++ b/packages/core/src/js/wrapper.ts
@@ -729,7 +729,7 @@ export const NATIVE: SentryNativeWrapper = {
       return RNSentry.popTimeToDisplayFor(key);
     } catch (error) {
       logger.error('Error:', error);
-      return null;
+      return Promise.resolve(null);
     }
   },
 
diff --git a/packages/core/tsconfig.build.json b/packages/core/tsconfig.build.json
index b5b1127a11..90d9d08e63 100644
--- a/packages/core/tsconfig.build.json
+++ b/packages/core/tsconfig.build.json
@@ -26,7 +26,6 @@
     "module": "es6",
     "skipLibCheck": true,
     "strictBindCallApply": true,
-    "strictNullChecks": false,
     "importHelpers": false
   }
 }