Hi there. Did you "Floss" your bobbin? Before I put in a new bobbin, I run a business card under the outer tension -- it's amazing how much gunk accumulates in there. And I also clean it with a lint brush between bobbin changes. Another fun thing I do -- If they are cardboard sided bobbins that are having the problem, I peel the cardboard off and run 'em sideless. Sometimes the cardboard gets bruised, for lack of a better word, and the bobbin thread just doesn't come off evenly. In some places the cardboard might be indented and impede the progress. Hey, anything's worth a try, right? lol Good luck! Judy