the thread is bunching on underside of fabric it looks like birdnest?

I have a singer touch tronic 2001 the thread is bunching on underside of fabric and unjamming what can the problem be?
Gloria Scott, April 2020


done
sounds like a drive belt is ripped to bits, you will too get a good look at it,

Michael Farrelly, April 2020
link Click here to see other fixes for Singer.