SAP Message WU539 - A different external vendor is assigned in the reference plant

Diagnosis
An external vendor that differs from the external vendor for thereference plant was found for plant &V4&, material &V2& in unit ofmeasure &V3&.

System Response
Price activation at plant group level may lead to incorrect results forplant group &V1&.

Procedure
You can activate prices at plant level by changing the price activationtype for plant group &V1&. To do this, change the price activation typeindicator to "Plant" in the plant group overview.