Hoover SE220 motor speed

My Hoover SE220 machine is 5 years old and has been no trouble until recently. It was not spinning properly and eventually not even turning over properly. Also there was a crackling noise during running. I had the back off and checked the motor during running when there was obvious arcing at the commutator. I changed the brushes for new and cleaned the commutator. However now, when on the wash part of the cycle, the motor runs at high speed for a few seconds, then reverses at high speed for a few seconds and so on; almost as though it is doing its normal wash cycle but at high speed. Probably because of the high speed, the tub vibrates terribly whenever it is turning.

Any ideas?