I had a similar issue with my havoc 3S/ballistic. Wasnt taking any ungodly jumps, but i noticed it after some of the bigger one.

It turns out for some reason, the sensor wire was wiggling itself loose from the motor. Would only do it every other heat or so...

My fix was pretty painless though, i turned the wire around and it stopped doing it. It grabbed on to the other plug better. I didnt see any obvious difference between the ends...