GR Based IV flag issue in PO

HI Gurus,

SAP SRM system details: SAP SRM 7.01 (extended classic scenario)

Issue: Inconsistent behaviour of GR-IV (Confirmation based invoice verification) indicator in SAP SRM7.01 system.

We are facing Inconsistent behaviour of Vendor flags in Purchase Order sometimes po line item defaulted as no GR_IV flags(2waymatch) and sometimes yes (3waymatch).We can see no pattern or cause, the outcome appears at the moment to be random.

Note: Vendorflag is checked for all suppliers.

Regards,

Anjan