I had problems with my thread breaking also. I changed needles, different thread, different batting. It would always break. Could do straight stitch with the sandwich no problem.....fast slow it didn't matter. Had a talk with my dealer, he recommended usung a good polyester thread, gutterman or Madeira, and to go at a fast speed. With the sample I had it worked!!!!! I really do like the machine, it has some wonderful features. I will keep following this thread, hope to gain more insight.