I know that you are going to think I didn't read your problem, however, every single time my HV Sapphire has had a problem its because I had the thread come off the hook. Try rethreading your machine and I swear I'm not nuts, but I have taken my machine in when I first got it. They messed with it at the shop and couldn't find anything wrong with it and then I was told by a wise gal, rethread it. I did and I've been sailing since,