desperate times call for desperate measures lol. i wish I had an idea but I'm coming up blank. Something is allowing the motor and/or pinion to move side to side or something is letting the spur gear do that. What I can't say and I've never owned an xmaxx so I dont know the rig very well.
Have you...
Hmmmmm, I swear I had a kit at one point that was doing that same thing but I dont remember what it was or how I fixed it. I want to say (IIRC) that in my case the fluctuation wasn't enough to cause an issue so I just picked a middle ground with the mesh and ran it like that. I'm not sure how much...