I am trying to edit a purchase order to remove an item that the vendor no longer sells. However, when I go back into the PO I am receiving the following error message "Receipt of goods 007807 in batch is currently referencing this purchase order". 

I double checked Receipt of Goods Entry and Receipt of Invoice Entry to see if there were any batches open but there isn't. We have confirmed that this particular PO was partially fulfilled on January 11th.

How am I able to fix this error and go back into the PO to make changes to it?