[CI] EqlSearchIT testMultiValueFields failing

[andreidan]

Build scan:
https://gradle-enterprise.elastic.co/s/xjdf5a7swa5sq/tests/:x-pack:plugin:eql:qa:mixed-node:v7.15.0%23mixedClusterTest/org.elasticsearch.xpack.eql.qa.mixed_node.EqlSearchIT/testMultiValueFields

Reproduction line:
./gradlew ':x-pack:plugin:eql:qa:mixed-node:v7.15.0#mixedClusterTest' -Dtests.class="org.elasticsearch.xpack.eql.qa.mixed_node.EqlSearchIT" -Dtests.method="testMultiValueFields" -Dtests.seed=720B9D4892B62FD9 -Dtests.bwc=true -Dtests.locale=es-US -Dtests.timezone=EST -Druntime.java=11

Applicable branches:
master

Reproduces locally?:
Didn't try

Failure history:
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.xpack.eql.qa.mixed_node.EqlSearchIT&tests.test=testMultiValueFields

Failure excerpt:

java.lang.AssertionError: For query [PROCESS where between(process_name, \"w\", \"s\") : \"indow\"]
Response does not match:
                             0: expected String [121] but was String [120]
received [1] more entries than expected

  at __randomizedtesting.SeedInfo.seed([720B9D4892B62FD9:7BAB01D6F0A15323]:0)
  at org.junit.Assert.fail(Assert.java:88)
  at org.elasticsearch.xpack.eql.qa.mixed_node.EqlSearchIT.assertResponse(EqlSearchIT.java:355)
  at org.elasticsearch.xpack.eql.qa.mixed_node.EqlSearchIT.assertMultiValueFunctionQuery(EqlSearchIT.java:324)
  at org.elasticsearch.xpack.eql.qa.mixed_node.EqlSearchIT.testMultiValueFields(EqlSearchIT.java:134)
  at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java:-2)
  at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:566)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.invoke(RandomizedRunner.java:1758)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$8.evaluate(RandomizedRunner.java:946)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$9.evaluate(RandomizedRunner.java:982)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$10.evaluate(RandomizedRunner.java:996)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.util.TestRuleSetupTeardownChained$1.evaluate(TestRuleSetupTeardownChained.java:49)
  at org.apache.lucene.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:45)
  at org.apache.lucene.util.TestRuleThreadAndTestName$1.evaluate(TestRuleThreadAndTestName.java:48)
  at org.apache.lucene.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:64)
  at org.apache.lucene.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:47)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:375)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.forkTimeoutingTask(ThreadLeakControl.java:824)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$3.evaluate(ThreadLeakControl.java:475)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.runSingleTest(RandomizedRunner.java:955)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$5.evaluate(RandomizedRunner.java:840)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$6.evaluate(RandomizedRunner.java:891)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$7.evaluate(RandomizedRunner.java:902)
  at org.apache.lucene.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:45)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.util.TestRuleStoreClassName$1.evaluate(TestRuleStoreClassName.java:41)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.util.TestRuleAssertionsRequired$1.evaluate(TestRuleAssertionsRequired.java:53)
  at org.apache.lucene.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:47)
  at org.apache.lucene.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:64)
  at org.apache.lucene.util.TestRuleIgnoreTestSuites$1.evaluate(TestRuleIgnoreTestSuites.java:54)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:375)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.lambda$forkTimeoutingTask$0(ThreadLeakControl.java:831)
  at java.lang.Thread.run(Thread.java:834)

[elasticmachine]

Pinging @elastic/es-ql (Team:QL)

[gwbrown]

Muted this test in #76623

[astefan]

I think I know why this happens, it might be the order (undetermined) in which multiple values of the same document and same field are indexed. Will investigate.