Originally Posted by JJs

Is the bat polyester?
Is the thread poly wrapped cotton?
Is the thread poly?
Is the backing a sheet with poly content?

Sometimes those things make a huge difference/problem.

Poly bats can cause thread to shred then break- so examine the thread to see if it's breaking or shredding.

Or if this is your first time trying to machine quilt, you may be moving the quilt too fast or two slow....

Or it may be that you just aren't holding your mouth right...