Twitching is bad. Its probably got a bad gear or the case may be broken inside where the little pin that the gears ride on goes in. That is a problem Ive heard of before. I had a 1313 that would do that on steering. I sent it back and they sent me a new one.
Spektrum will cause glitching if you have the RX and TX within about 3ft of each other but thats a glitch where the servo would normally just do it once in one direction and then stop rather than bouncing back and forth.