Can honestly say thats never happened to any stock Moto devices I've owned or my friends have owned. It's only happened once and that was from running a buggy CM10.1 on the RHD (not Moto's fault). I'd say replace it, that's pretty unacceptable.
Also you only need to hold power and volume down for like 7 or 8 seconds, it's a simulated battery pull, since these phones dont have removable batteries.