I found out that monofilamenty thread can be a problem although I use it a lot on charity quilts. I learned never to use my thread cutter with this thread. It popped back and wound around the tension and this just froze my machine. After two trips to the repair shop and it was explained to me, I'm more careful. I use it on the top but not on the bobbin. So far I have had no problems. Just use care!