When you create a process step that uses the Copy Task WBS From Template System Action, you cannot delete tasks from the Template Task External ID field.
Steps to Reproduce:
Expected Results: Task should be removed successfully.
Actual Results: Task is not removed.
This was analyzed by Engineering under CLRT-40749 / CLRT-52595
Release: Any Clarity PPM release
After Engineering's careful review, it was decided not to make changes to the product area affected.
Resolution: Delete the step. Then recreate the step with the desired tasks included.