Partner role & not defined in partner schema &

What causes this issue?

The system has checked the arrangement partners for rebate arrangement
&V3& (e.g. for the functions "Extend" or "Create with reference").
In the process, it discovered that partner role &V1& in partner schema
&V2& is not defined.

System Response

The function you invoked was performed successfully, but the partners
belonging to partner role &V1& were deleted or not adopted.

How to fix this error?

Please check the rebate arrangement partners.

Error message extract from SAP system. Copyright SAP SE.