Happened to me to, but the other tunnels work fine. Speaking of tunnels, that would be a great idea for a large team deathmatch. Just have one squad at one end of the swamp, and the other at the opposite side. Each time has a boat and a mounted machinegun at their starting point. Of course, you can only go a maximum of 5 meters away from the swamp or you are automatically killed. The caves would definitely make for some good CQB.