I think that I may have the same problem. Have a Pfaff 7570 and when I am doing SID every once in a while I get a loop on the bottom. I think it would be wish to invest in a new bobbin case. I was given the machine so no telling how many stitches have been sewn on her. I am going to check it out right away... Thanks so much for the suggestion! :thumbup: :thumbup: :thumbup: