I understand the thread cutter problem.
This happens usually if I am using a thin thread like Bottom Line and the needle hole size is too large, changing to a 80/12 (or smaller) topstitch or Microtex needle usually helps this problem,
There is also the possibility that you can get this adjusted (make the length longer before it cuts) at the shop when you have it cleaned - I was told this by the dealer when I got my machine.