
If someone has re-opened a closed purchase order via View Purchase Order Receipts, those items now re-appear on the report, but should not. If you go back and close this purchase order, they will disappear from the report.
If a wrong part number or qty was received and a correction processed so that you have 2 transactions that net to $0, you can just enter a dummy invoice for $0, and select both of these offsetting transactions to clear them (I think you have to select the credit transaction first, i.e. negative dollar amount)
I balance this report monthly to my open packing lists, so I come across some unusual items frequently.