Diagnosis
Correction items always bear a reference to an asset. In one asset, thenumber of the business entity is saved in the "Super Number" field inthe Real Estate objects.
You have probably tried to assign rental units to a correction itemwhere the asset refers to a business entity to which the rental unitsdo not belong.

Procedure
You can only process rental units that can be assigned to thecorrection items. You have to make a new assignment for the otherrental units.