Confirming. I have had 2 cases like described...in air. Don't know if gods at my side were from ancient Greek or from somewhere else :) but I managed to save my copter somehow (deffective motor started again after taking throttle to 0 and then to max). It didn't happen on 3-d time!
Cause was a motor wire soldering covered with heat -shrinking tube. It was mechanically ok (couldn't tear it apart) but cutting off the tube revealed a poor soldering, probably due to too much heat applied during shrinking the tube.
As they say - electronics is a science of contacts....