Anyone have trouble with the 1UP anti-wobble/security mechanism loosening up on rough road?
If you're talking about the locking bolt through the hitch receiver, then yes. I think this is a real design flaw of the 1up racks (or maybe the idea of 4wd in Wisconsin is a bit different than the West). Either way, get a hitch stabilizer plate. It will stop the side to side play that causes the bolt to loosen itself. I've never had the locking ball come loose, though, and that's with a lot of rough 4wd and 3 bikes on the rack.
Also, if you're carrying a mountain bike with typical wide bars, be very sure that you have enough clearance from the back of your camper. Like a number feet. For some reason the 1up racks tend to have a lot of vertical (front/back) play. I learned the lesson the hard way with damage to the back of the camper and a shattered rear window after a particularly rough 4wd road. Not what you want to realize when you pull into camp.