I vote for a bobbin issue, I have 2 Pfaffs (older, nothing fancy) but the bobbins seem finicky. One of them winds the bobbin too full and I have to remember or else take some thread off. Also make sure you are putting the bobbin in correctly, it seems a little different from my Singer. If nothing helps, take it back and let the shop help you. I would call them if it is too far to drive today. Good luck with getting things straight.