Ebike Won't Stop

I helped a friend convert a cruiser bike to an ebike with a Bafang Mid Drive kit. Occasionally his bike goes rogue and the motor won't stop moving the bike even when he stops peddling. I don't think the throttle is even installed. His brake sensors are not installed either.

Has anyone heard of this happening? Any ideas of what the cause could be?

Thanks!

* This article was originally published here