The week day for service &2 of service frequency &1 is incorrect

What causes this issue?

You have attempted to change a week day for service &v2&. However, you
have not selected the <ZH>Variable service date</> field for this
service.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

INCLUDE ISU_KORR OBJECT DOKU ID TX

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.