So I picked up a roller controller recently and found that "down" doesn't work. When you roll the ball in the down direction, the icon on the screen goes up. Up, left and right work fine. I thought this may just be an issue with the rollers inside the controller, so I cleaned those and oiled the bearings. The controller feels nice and smooth now, but it didn't fix the issue. I cleaned the optical sensors as well with no luck. I did notice that a couple of the bearings were starting to rust, so it's possible this thing was exposed to water at some point. Anyone familiar enough with these things to know where to look for the issue?