Rel.maintenance not possible when using maintenance strategies/packages

What causes this issue?

You may not create relationships between operations if the operations
are based on a maintenance strategy or maintenance packages. However,
you tried to create relationships for operation that are assigned to
maintenance packages.

System Response

the system accepts either relationships or maintenance packages for
relationships, but not both at the same time.

How to fix this error?

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

Error message extract from SAP system. Copyright SAP SE.