When going up a steep-ish hill, I have on a couple of occasions nosedived and ended up bailing. No big issue there, I understand why and generally land on my feet. What IS a HUGE problem is that if the OW ends up on it's wheel, and angled downhill, it will start to take off. The crash disengages the wheel and it will quickly speed up faster than you can catch it.
The first time this happened to me, I was fortunately in a park and it flew (going really fast) into the bushes with no consequence. The second time I remembered to run quickly after it and caught it after several yards.
If this happens on an occupied street, there is a strong likelihood that it will careen out of control until it hits a car or worse a pedestrian. The behavior after a crash should be engine breaking, not free spinning. Should be a relatively simple firmware fix. But someone will trash a car or a pedestrian eventually if this isn't done.