While you wait for answers, we may have found some information which could help you.
Click here for Sewing Machine Singer Bobbin
Singer 201 went bang , smelt and now won’t work?
Bobbin won't wind?
My CG 500/550 Singer Sewing Machine's bobbin isn't working?
Presser foot is loose?
Singer 507?
the thread is bunching on underside of fabric it looks like birdnest?