On one machine it did / does the same thing. A couple of times they back lashed in the bobbin case for a real mess. So i tried what i seen Trox i belive it was said. Go around the tension one and a half times then to your bobbin. So far it has helped. But i have had spools of thread that just wouldn't come of the cone right. Not sure if they weren't wound right or what. Sewing their fine but won't wind for a bobbin worth a crap.