I agreed with Maciej that this is a serious issue. I don't like work arounds. I know that this affects some more internal things. One more reason for me too fix this as soon as possible. It will only get more difficult if you postpone this. IMHO this is a design problem. Could you point out the differences a bit more cleary, Huisheng Xu? When and where are you taking care of the tasks which stays in the left after the execution is triggered?