Hi rbrown
First of all I'd suggest checking the transactions recorded involving this item and account y, if any of the transactions are inventory adjustment, the allocation account would be manually entered at the time recording.
If they are item invoices/bills, the linked income account for that item could be set to account y at the time, please look up the transaction in Find Transactions which will display the accounts posted to when the transaction was recorded.
With the current linked account set to x, you can enter a dummy item transaction, before recording it use Ctrl + R to recap the transaction, which will show the accounts being posted to upon recording. If the recap is correct then the set up is done correctly going forward.
I hope this helps, please feel free to reach out if you have any other questions.
