Subobject &1 &2 &3 already exists for a different IMG activity

What causes this issue?

The direct maintenance of sub-objects in not possible, since an
assignment for a different IMG activity exists:
Object &V1&
Object type &V2&
Sub-object &V3&

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?

Maintain the sub-object with transaction <DS:TRAN.SOBJ>SOBJ</>.

Error message extract from SAP system. Copyright SAP SE.