Message SAP WU876 - Product group &2 for offer &1 contains differing offer types

Diagnosis
The offer type, unit of measure, price, percentage discount, andabsolute discount of offers that bear the same offer ID, must correspond(depending on the offer type). You should create offers with an offer IDin promotions, in which offers with an identical ID but with differentcharacteristics are already available.

System Response
The system rejects the changes.