Snapped needles are the most likely thing that could happen.
Sometimes people assist the motor by turning the hand wheel, and I've heard that can bend the frame of the sewing machine in some cases. That'd be the most catastrophic failure potential I think
I'm truly glad that it's helping someone; however, for every one of you there are a hundred people denied important procedures because insurance has decided its opinion is more important than the doctor's.
An easily available example off the top of my head is Styropyro's most recent video where he might have cancer but Insurance has denied his brain scan.