Hi,
Please check in the Access seq . Drill down to the Access/field. You will find a button for field catalog.
Check if KNDNR is added in the field catalog.
And i think KNDNR is something related to COPA.
Do you really find a field KNDNR is the Sales order? I checked in VBAK/VBAP. I wasn't able to find it.
Please check the below link
https://scn.sap.com/thread/1746259
http://www.sapfans.com/forums/viewtopic.php?f=5&t=245516
Regards
Dhilipan