I would change thread brands. I bought a Janome 6600 last fall and was about to tear my hair out. It despised Guterman thread. I fought and fought with it. Finally, it was suggested that I use Aurifil~not a problem since. She also likes Superior and Anton Robinson...go figure! I also bought some of those tiny little white teflon washers that fit down in the bobbin case. They seem to work also.