I think I got it. It WAS related to "Please choose an item to add" message. I was iterating beyond the number existing line items on the PO. Once I put a limit on the lineItemCount, it seems to work. BTW I still get the "warning Items on this line have been received. Are you sure you want to modify it?" message but now the record saves as @k1ko mentioned originally. Thanks for all the help. Learning A LOT on this slack team/channel!