Trading partner automatically populated for document type KP

Hi All,

We have two vendor A & B. In vendor A master data we have trading partner maintained & in Vendor B trading partner field is blank. Now when we execute transaction MR11(GR/IR clearing) then trading partner is populated to both the vendor. Which shouldnt be the case. Vendor A should display its trading partner and Vendor B Traidng partner should be blank. but it is displaying Vendor A's trading partner to all the vendor in that particular document.

Can any one help in this issue?