Just a pilot, but read the SB- basically requires inspection of the jam nut and lock-washer at the bottom of the servo rod. Should be safety-wired and have slippage paint mark.
Looking that servo during the preflight this morning was chilling. *IF* that lock-washer/jam nut weren't secure, the servo extension rod could twist, back off, and finally disconnect. It seems that this very event has occurred previous to this crash. If that happened, you'd lose the load-damping effect of the servo, the controls would have an extra hinge between the push/pull tube bell crank (or Richard cable end?) and the point where the servo housing attaches to the stationary star. The lower servo mount aligns the servo and all control input are thus restrained and aligned in the vertical. I'd guess (I'm only a pilot) that the effect of the mount freeing would be a lot of feedback in one axis and a sloppy controls in the same direction, until the new hinge in the control run failed/jammed? Joe Sulack did a heck of job getting it back as far as he did.
That servo rod is very smooth, designed to move freely in housing. The jam nut/lock-washer combination are the only rotational restraint on the servo rod to the banjo(?) fitting.