Error when trying to delete a vendor from SC

Hi all,

I am encountering a problem when trying to delete a vendor from a contract and assign preferred vendor.

The messages are

"Enter exactly one partner of type preferred vendor"

"Partner data couldnot be determined".

In BBP_PD, I find two entries in partner table with partner_fct = 39.

I am also not able to delete one of this entry.

Please suggest.

Thanks

Nandalal