Had this happen to me in the Main. 3 heats, seem to be okay, it the main, first lap came to the end of the straight away, it the break a little hard to get through the sweeper to the double, pop. belt came off. One of my pit mates took it apart, we believe it was the break force that might have been doing it. we got it back together, ran it pretty hard and not slip. We backed off the brake force to 25% on esc and 89 on the controller. I did order a new belt and pulley just in case. but again we ran it pretty hard and did not pop off. Again thanks to fastpede for checking it out with me.