If your issue is with the fabric, (I assume you meant muslin and not Muslim) you might want to experiment with other brands or weights of thread. You don’t say what type of thread your having issue with, or what machine your using. A little more info would help us help you. Are you using the same thread on top and bobbin?
FWIW, my Fusion is persnickety and only likes cotton thread, King Tut specifically and I’m ok with that. Tension can be picky, but the more info we have the more responses you may get.