Are you using a sharp needle and not Universal or ball point etc. With my Bernina, I don't have any problems (better knock wood since I'm starting a new batik project) when using a Schmetz 12 jeans 80/12 or a Schmetz Microtex Sharp 80/12. I find that Coats & Clark thread doesn't do well in my machine. I use YLI and Sulky with success.