SAP Message TWBHS044 - Test plan can only be changed in system &1

Diagnosis
The original system of the test plan is system &V1&.

Procedure
Change the test plan in system &V1& and transport it into this system
or
Change the test plan in this system using function "Change WithoutReference to the Template". Only make urgent repairs here and alwayscopy changes to the original system of the test plan.