Originally posted by LDM
Could the tightening of the screws caused the gear to stick due to the possible uneven surface ?
Yes!
Fortunately, there's an easy fix.
Smear some wood filler on the rails, then cover them with waxed paper. install the retracts, but don't tighten them down, just lightly snug, and let the filler completely dry (overnight)
The filler will now fill the unevenness, and you should be able to tighten them down without binding.