We may have found other answers which could help you.
Click here for Seem Machine Sewing
the thread is bunching on underside of fabric it looks like birdnest?
Singer zigzag 457 Stylist not threading bobbin/making stitch?
Presser foot is loose?
Singer 188K1 presser bar stuck?
Singer sewing machine 626 kno?
Singer 201 went bang , smelt and now won’t work?