SAP Message RESCSU066 - SU &1 is for directly assigned costs - SU &3 already exists for RO &2

Diagnosis
Settlement unit &v1& was assigned to a service charge key in which theindicator for directly assigned costs is set.
Rental object &v2&, however, is also assigned to settlement unit &v3& inperiod &v4&. Settlement unit &v3& has the same service charge key assettlement unit &v1&.
Double assignment is not allowed.