Check the type of thread you are using.....I have a Topaz 30 and it was doing the same thing a few weeks ago. I called the shop and talked to their tech and that was the first thing he ask is what brand of thread I was using. I changed to a spool of Mettler and it worked fine. I used it to sew a few seams and changed back to Coats & Clark and it has been working fine since. What sense it makes is beyond me...