In the first, third, and last cases the vehicles pretty much crashed into people. Two appeared to be equipment failures. The first looked like a GPS failure, the latter was a motor failure. I have two unexplained equipment-related crashes with my large Cinestar hexarotor, which has been enough to make me decide to never fly near other people.
And while RC drivers like to downplay the "drone" aspect, many pilots are hopelessly dependent on GPS position hold, in which case the vehicle essentially IS a drone, and is flying autonomously. When that malfunctions, bad things happen.