I have that machine too, bought used, and have been trying to figure out what the problem is. I have used a lot of different needle/thread combinations, using all the holes, two of them, running thread backwards through them, a thread stand, cones, etc. I do better with Isacord so far, as Leah Day recommends and says that she went with the Isacord because of thread breakage and said some machines just like to break thread if going in a certain direction. I also notice with my particular machine the problem is more pronounced when I move the sandwich to the left. I am trying very hard not to pull it through and I have the whole thing well supported. Someone on the Facebook pager this machine had the problem after quilting many quilts successfully and found a tiny burr in her needle hole and had some products up that I can't remember that she used to smooth things out. I haven't tried that. I clean and oil my machine regularly and it does a great straight stitch and sometimes will go for a long time without shredding/breaking the thread. So it is a mystery to me too. I do have slightly better results with the Juki open toed foot vs. either one of the two Brother feet made for this machine. Could be coincidence. I hope one of us figures it out!!