After driving a bus from Vavilovo to Gorka, my friend and I encountered a sudden fps drop. We were then both kicked by the server due to

Signature check time out

We decided to try again, but were unable to play on the same server again, since the problem occured every time we joined the server (in the bus' vicinity).
So we met on another server, ran a few meters away and changed the server again. When approaching the bus, the problem was still present, if you were closer than around 50 meters.