I was going to ask the same question. Are you sure you have the right bobbin?
I pulled out a bobbin the other day that I swear was for my Pfaff. It doesn't fit correctly. I got out my calipers, measured, and realized that the diameter was correct but the thickness was incorrect. I suspect that somehow I got a bobbin from someone else's machine mixed in with mine from a class. I don't own any machines other than Pfaff. Very frustrating. I wonder who has MY bobbin and if they think their machine is broken.