Can't modify a SRM PO

Hi, I'm using extended classic scenario, I have a PO with 1 service line and 11 direct material lines, the PO was authorized and replicated to ECC, and there we made material and service confirmation and invoice registration, we realized that the PO had a mistake and we were forced to erase the confirmation and invoice documents, then we accidentaly marked the first line to be erased and the document got authorized like that, if we try to erase the whole document it throws a backend error regarding an invalid account assignment and can´t be modified. what can I do?? please help me.

Fernando Fonseca