Originally Posted by
RVDT
The bearing is seized in the rotational sense as it isolates the static and rotational part of the control.
I may have misunderstood, but doesn't the duplex bearing also help transfer the horizontal load from the static to the rotating part?
If the bearing fails then a number of possibilities then exist. Losing the nut at either end is one, but a misalignment of the static rod leading to it jamming is another.
The servo may run hard over, or may run to neutral depending on how the feedback control is connected. I don't have any details of the servo to be able to say with certainty.