This does not solve the problem. As you can read in the issue tasks belonging to an execution cannot be deleted and should not be deleted like this because valueable information is lost in this case. The attached patch by Ronald takes care of all the problems. It does not add a new feature but corrects a bug and makes the engine's behaviour correct. Without this issue it is not possible to use a timer on a transition coming from a user task. So why start looking for workarounds if there is a complete patch available? If it works for you and Maciej as well it should be committed I think.