I have a Bernina 830 and love it, I was told that if I used polyester thread on my Bernina there would be less issues with the thread breaking. I just use polyester thread and have had no problems. Rayon thread seems to be one of the worst for this problem, and some threads have little bits of lint that come off no matter what you do. You should be oiling your bobbin area, each time you change your bobbin, just a drop of oil inside the area where the bobbin fits will keep it lubricated, and be sure to use your bobbin tool to clean it regularly. Please keep going back to your dealer and letting them know how frustrated you are in attempting to deal with the issues you are experiencing - and make sure you keep track of the dates, times of your calls or visits to the dealer along with the problem. Do not give up on your machine. I hope you can get past these issues.