Some PO Releases Don't Close Automatically

I have a BAQ I’ve written looking at open POs only. I then show all releases on these open POs. I’m finding some releases that are received, arrived, and invoiced but remain open. What would cause this to happen? There are some from the same PO that closed automatically just fine on the same receipt. What gives?

Check to see if there were multiple receipts for those lines. I seem to recall a bug that would not close a PO Line if it was fulfilled by more than one shipment.

It was a good thought. But I picked out one example and it was only received on one receipt. Worse yet, a different line on the same PO did have multiple receipts against it but that one was closed!