P0411Z1 Voucher Correction

During the E9.20 upgrade implementation an A/P user is trying to modify an existing, unprocessed voucher record in P0411Z1 that was uploaded via the EDI process. The Supplier field as well as a number of other fields are greyed out. They maintain these fields are editable in their instance of E8.12. My experience has been that once the F0411Z1 & F0911Z1 records are created, the key fields such as company, Doc Company, Supplier Number, etc. are locked to maintain integrity. Only the Invoice #, Invoice Date, amount, etc. are editable. To correct the Voucher needs to be copied and updated