I use the needle up/needle down exclusively. I think it's just a flaw with the 6600. I had a Viking before this and RARELY have this problem. The 6600 cutter cuts the threads too short and the thread must recoil somehow if you dont do everything just perfect. If I could get another machine with the same options for the same price, I would dump the 6600 for this reason and a few other things that are just poorly planned.