It threw me for a loop too, literally! [:@] (I didn't diagnose the problem until the plane went in one day.

I was making an approach towards the field at something over 1/2 throttle and the plane suddenly climbed, rolled over and went into a tree. Fortunately no serious damage.

I eventually found the glitching after repairs and putting the plane and radio gear through a real vigorous range test, including running the engine at various throttle settings. When badly jittering servos showed up repeatedly right around 3/4 throttle, that's where I focused my attention, and changing out the cable solved the problem.
Dennis-