Hi Logan - suggest that you try Glen's idea first. I backed off the bearing preload on my (similar) NEQ6 when the dec got too hard to move freely and it worked fine thereafter.
I don't have the mount in question, but think that the nut shown in the very first part of this video is the one to loosen a little bit (after backing off the locking screws as shown) and then gently tighten it back up to the point where side play is gone, but the axis still rotates freely.
https://www.youtube.com/watch?v=Cp3Vq_6G5bg The video doesn't show how to get the end cap off to get at the nut, but hopefully that shouldn't be too difficult.