Does the servo glitch (delay) immediately or only after going full lock on the steering, could be that you need to adjust your EPA so that the BEC doesn't brown out if the servo is binding under excessive load at full lock.

Is the servo simply "jittery"? Perhaps a video showing what's going might be helpful, some servos are more jittery than others.

I would also rebind your Tx/Rx as well as recalibrate the ESC if it's been a while since you last used your electronics.