steering servo very "jerky"?

[Monkeysmate]

I've just rebuilt one of our cars,and i've noticed that the savox digital steering servo is visibly "jerky" or notchy through the range of movement, like it's moving in little steps, rather than smoothly.

I've disconnected from the steering mechanism, and it still seems notchy with just the servo horn attached.

Any thoughts?

Does anyone have any ideas what may be causing this?

Thanks