I dont know how new PvE content was tested coz there is very painful bug on BETA lair mission, which makes impossible to complete it on hard. So, lets proceed to the main point. After big room with platforms, where you must transport power 2 cells, there is stage with corridors, where you can turn on your first right, jump into the hole on the floor, into sewers with mud. Its what on normal beta map. But on hard there is invisible wall, which you cant pass whatever you try. Only way that is left is try detour way. Unfortunately, on that way you must cross little pool with mud. Its bugged too. Once you step into it, you cant get out. You simply cant climb over the edge of platform. There is no way you can reach exit at this part of map. After time runs out -> you lost Here comes tip: You need one player with jumping class (assault/raptor/hawk/stormboy). After you get into pool with mud, walk close to the wall and press space (dodge button). Mud in this pool is bugged too, so you will be able to jump out from pool. After that, just run to the exit. If you are lucky, you'll be able to get there alive.