How are you doing AlvaStitcher? I don't know if you have had a chance to do anything to your machine yet, but like metioned, brand new bobbins can act up. With 66 bobbins the probem has mostly been not going on the winder properly, the inside has been finished off too roughly to slide on at all in some cases. The have all worked fine in the machine, nicely polished and with an accurate fitting in the bobbin case.