I have had the same problem and finally took my machine in for a tune up. What a difference it made. I had struggled through several quilts with broken needles, skipped stitches, and breaking threads. Everytime I would think I had the problem figured out, I would encounter another problem. Sure wish I had just taken it in sooner. Now I can even use those thread brands that I would never have tried before. Maybe it is just time for a tune up for your machine also.