Diagnosis
You are trying to process a batch of the material &V1&. Of theexisting batches of this material, only batch &V3& is classifiedin plant &V2&. This batch is currently being processed inanother session. To prevent both batches from being assigned todifferent classes, you cannot process other batches of material&V1& as long as the batch &V3& is being processed inplant &V2&.

Procedure
Finish processing batch &V3& of material &V1& in plant&V2& in one of the parallel sessions.