The results show that the fracture may be due to improper heat treatment which leads to over hardness of the thread part and the joint of thread part and tooth part.

Enables multiple collaborating objects to participate in a single transaction, by passing the transactional context as part of the thread.

Now the UI is safe and the code is simpler, because it separates the work into the part that should be done on a worker thread and the part that should be done on the UI thread.