The servos on my plane were jumping too. Just the rudder servo actually. I decided to "live with it."

Then I broke the front wheel off my landing gear, and I decided to redo my control rods and make it steer better. Once I finished all my work, I removed some binding on the control rod. Not much, but still some. Once I did that. The jitters went away.

Simple test, remove the control rod connection to the servos. THen turn everything on. See what happens.

Good luck.