Diagnosis
The entity &V2& of entity type &V1& has been added again to changerequest &V3&. However, you have not yet saved the change request &V3&.Entity &V2& of entity type &V1& is therefore still locked in changerequest &V3& and that is why it cannot be created or changed in singleprocessing. The same applies for mass change.

Procedure
Save change request &V3&. You can then process entity &V2& of entitytype &V1&.