Troubleshooting AC motor brake
As noted by others you should try changing the brushes. I had a washing machine with a universal motor stop working. (No notice, just went from working normally to stopped mid-wash.) The brush and commutator surfaces showed no signs of damage. The only visual indication was that the brushes were much shorter than a new pair. Fitting new brushes restored normal operation. So compare your brushes to a new pair and replace them if noticeably shorter.