Associated object type & cannot be deleted

What causes this issue?

Associated Object Type cannot be deleted.

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?

The Object Type is maintained as sub object in the sub node. If you
delete the entry from main view then, data inconsistency may occur. To
avoid this, please delete the entry from the sub node and then try to
delete from master view.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.