Breaker is Tripping
Usually breakers do not go bad. If they repeatedly trip, they will need to be replaced because the breaker gets weak but if one trips, something else is behind it.
First check the walking belt and deck. If you have recently adjusted the walking belt or motor belt, make sure you haven't overtightened the belts because this can cause the breaker to trip. A worn belt and/or deck is the problem about 80% of the time.
Check the motor for high resistance. If the motor has started to cook itself, it will build up high resistance which relates to high amps which can trip the breaker. Look for signs of charring on the wiring and connectors.