I have to admit I don't travel with mine much as it is a heavy machine. I have a rolling tote for travel but still prefer to sew at home. I also have NEVER used a prewound bobbin in my Bernina, are you sure it is the right type bobbin for the machine? I have always been a bit leary of prewounds. When you had the trouble did you take out and clean behind the bobbin race? Sometimes a little piece of lint or thread can get trapped in there and cause problems. Good luck with this - hope you find a fix for it soon!