My experience with throttle control troubles comes from other peoples' experiences since I have not had any problems so far. I have Futaba S148 or S3003 servos for throttle. Most of what I have seen with gassers is that either the throttle linkage or the servo mounts fail, causing loss of throttle control. As a safety requirement, our club insists on having optical kill switches linked to one of the radio channels so that the engine could be shutoff during flight in case of throttle control loss.