I have that same machine, now about 5 years old, and started having problems with the thread knotting up on the bottom at the beginning of the seam and then it sounds like it's chewing something up inside the bobbin case. I've had it looked at by two different Pfaff technician/service guys and have been told that there is no other adjustment to be made. I'm back using my 40 year-old Bernina, that never gives me any problems, but it doesn't seem like a machine that new that was quite expensive should be having any issue. I would never, ever buy another Pfaff machine.