Sub inventory stock allocation not working as expected.

Summary:

According to the picking rule setup, subinventory allocation is not being prioritized.

Requirement is stock should get allocated from one subinventory example X subinventory instead of Y subinventory

Content:

Business has a situation where LOTS with batteries whose shelf-life expiration is nearing by should 1st get allocated when sales order comes in.

So we created a subinventory and put those items which are expiring soon in that subinventory.

The subinventories have a picking order in place and the picking rule is prioritize with subinventory ascending.
We ran testing one time we have seen the stock is getting allocated out of subinv 467WL1ShLF (new subinv where items nearing expiration are placed) and we tested the second time and could see the system is not prioritize this subinventory although enough stock is present in that subinventory.