Sounds like the rest of your quilt is getting hung up on the edge of the table/in your lap/behind the machine/etc. When that happens, the needle can bend enough so it hits the throat plate and breaks. I'm no expert, but I've learned that before I begin stitching, I adjust the rest of the quilt so the area I'm working can be moved easily and freely. Hopefully some more experienced FMQ'ers will weigh in here. Karen