Value in Trading Partner field is 'NONE' in WE (Goods receipt)Document

Folks,

After posting GR against a Purchase order, trading partner field in the corresponding FI Document (WE) is getting updated with a value 'NONE'. Although a different trading partner value is maintained in vendor master.

Trading partner value is always 'NONE' in FI document type WE, nevertheless whatever value is maintained in vendor master.

Please let me know what's the reason for this?

Regards

Amitava