Pidog servo jitter (just one). Any ideas?

I zeroed all of the servos as directed but one jitters if the servo is pushed forward but stops if pushed backward. I am a new user so I can not upload a video showing the problem. this only occurs with one specific servo

Which part of the servo is shaking?
It is recommended to provide us with the problem video.
If the video memory is too large, it is recommended to upload the recorded video to onedrive and share the video link with us, giving us permission to access the link.