Hi M Sham,
Check in OVA2 for group B, procedure 33 - does it carry field KZWI1 w.r.t. VBAP and if yes what's the complete defination. Could you share screen shot?
If this field is not there cross check whether it was there when you created SO's in December and someone changed the procedure? Were all these orders were created at same time or after that.
Regards
Rahul