Can not delete object

If you are trying to delete 1 object in the workset, but get this message:

Can not delete associated feature 'ABC' (Result of task 'DEF'). It is not reserved.

then try to reserve the task 'DEF' first and repeat the delete operation.

NB! If this task is a WS task, please go to CAD, open the design dialog for this WS task and run "Tools", "Clean up...".

If you on the reserve operation get an error message like this in the process window:

Editing task 440 (Disposed) is reserved, while the appurtenant  netelement result 180 is read-only.

Then you need to contact support by sending an email to civil.support@trimble.com with the name of the project and the error message from the process window.