It's called "ADMIN BRAIN" bug.
Admin added map X to maps.lst but didn't upload it. So if you vote for it, it says "succesfully voted. changing map" but nothing happens. And then u can walk through each other, shoot railgun through body... . You can't use lift, u'll get stuck in it or you'll be left where you were standing.
It was found on Ergo Gibbus server.