If you disable "Show Model" for a manned vehicle either in eden editor or zeus, its pathing will be disabled. Giving a command still gets it to turn the engine on but that's it; as soon as you enable Show Model pathing resumes and the vehicle will move, but if you disable show model again it immediately stops.

Several people have been able to reproduce this with ease, without using mods.

If you remote control the unit with Show Model disabled you'll still not be able to move though (as if simulation was disabled), but the engine will still run

Due to this, all compositions that rely on hidden vehicles with attachments no longer work