I've seen several people complaining about grit getting into the center gearbox. I noticed a bit sneaking into mine as well. Based on what I saw when I dug into the center gearbox, the most likely entry point is the un-sealed area covered by the trap-door used to access the motor. I have a ton of miscellaneous Tamiya parts handy, from all those XV-01s I built, so I dug out a piece of soft adhesive foam padding and made a seal for that part of the trap-door. This should stop grit from sneaking in when the slide-out motor mount wiggles around inside the gearbox bulkhead. It might not be a 100% solution, but currently that area has no seal at all, so it will definitely be an improvement.
