I was just getting ready to tell you to take the bobbin area completely apart and clean it out but I see just above that you have done that. It took me awhile to realize after fighting my machine for hours that all I had to do is clean out that area. I always find a small piece of thread that was causing all these problems. So now every time I have to rewind a bobbin, I clean out that area and oil the specified areas and I don't have that problem anymore. I also don't use the cheap thread. You can really tell the difference between the type of threads.