I have rethreaded it several times. It is a Singer 2662. It is like the bobbin case is moving around when it shouldn't be. I had my dh come and look at it and he popped it back into place and get started and the tension is off again. I get it fixed, start sewing and then I hear a thunk and it is off again. Then I look and I cannot get the bobbin out. I keep having to get my dh to get it out with a screwdriver.