I suspect that the machine's timing is off because of it striking the bobbin case. I purchased a second case for my 6600 to adjust for applique and it only cost me $23. But that price could be based on my dealer bulk ordering those standard bobbin cases. If you were quilting with the blue marked case - yes, I have seen them go for nearly $60 when a dealer orders just one at a time.
You may have already taken these steps so I only sugguest them as a reminder... <G>I'd double check to be sure that bobbin case is threaded correctly and that it is seated in the carrage of the machine correctly. If you are using a heavy thread in the bobbin you might have to loosen the bobbin tension just a tad. Also make sure the needle is inserted all the way into the machine and tighten the screw with a screw driver rather than just hand tighten.
Let us know how things work out!
Janome MC6600, Bernina 240, Juki MO735 serger, 1948 Singer 15-19, 1950 221-1, 1951 201-2
08:59 PM by