I got my uConsole recently and I had this issue! I believe I am being sent a replacement trackball but something I noticed was that when I flashed a different OS onto a different SD card (specifically this one: Bookworm 6.6.y for the uConsole and DevTerm - #305 by Rex) , the trackball seemed to work better vertically.
It might have all been in my head but now that I am back on the stock OS it seems like the issues are back.
Weirdly I have noticed this issue in different directions at different times. Sometimes it’s all y axis movement. Sometimes it just doesn’t move up but it moves down fine. Sometimes it moves down but won’t move up (I may have flipped the ball around as part of troubleshooting). I have even had it refuse to move left, but not right.
What’s the common factor? I don’t know! I guess the way it works is with hall effect sensors, so it’s like a wireless voodoo trackball. Seems like there could be potential for physical interference, or maybe there is a firmware problem! I have NOT upgraded my keyboard firmware to the latest version yet.