Hi,
These are the instructions I recieved.
if obvious backlash can be sensed when shaking the mount, it means there is problem with the spring part on the worm and gear where is supposed to eliminate the backlash.
Please open the black plastic cover, and then move worm base A where there is a spring, by hand. At this moment, the worm base A can be moved freely. And when the hand is off, the worm base A will be pulled by the spring to the gear.
Basically you loosen the screw holding the worm in place, adjust the position and then retighten. This is very easy, but you need to check the movement through the whole range in case it binds anywhere, in which case you need to back off a little and perhaps accept a little backlash somewhere.
Hope that helps.