does the tub pulley show signs of slipping?
I had two that the belt kept coming off. One was the tub pulley (belt was slipping, need the pulley, nut and belt) Second one had a very small nick in the motor pulley and now and again the belt would catch the nick and it would pop the belt off. Can't buy just the motor pulley need the entire motor. Customer was going to live with it and just keep putting the belt back on.
I ordered the entire kit plus the belt cam kitbelt