Default Store is always used when retrieving sequence value's for sales entity's.

[reztierk]

The getReservedOrderId function in /vendor/magento/module-quote/Model/ResourceModel/Quote.php and the _beforeSave function in \Magento\Sales\Model\ResourceModel\EntityAbstract are using getStore()->getGroup()->getDefaultStoreId(), when they should be using getStore()->getStoreId(). Causing orders placed on other storeviews to use the prefix/suffix/increment id and sequence tables of the default store.

Preconditions

1. Magento 2.1.5

Steps to reproduce

1. Setup a clean install of Magento 2.1.5 with sample data
2. Add a second store view to the default website
3. Place an order on the second store view

Expected result

1. An increment id using the prefix from the new store view, and an entry in the sequence_order_2 table

Actual result

1. An increment id using the prefix from the default store view, and an entry in the sequence_order_1 table

[jaykobi]

Those line were introduced two years ago:
f9559c2
MAGETWO-36935: Orders placed in different store views should not have duplicated IDs

But I don't see why, either. With sequences and the meta table I can precisely crontrol when which increment id is used. But getStore()->getGroup()->getDefaultStoreId() completely breaks this for multiple store views in one group.

One more in the long list of bugs that REALLY need to be fixed asap.
Thanks for reporting @reztierk.