Once I anolyze the alien/human tissue in the wreckage I am to exit the room - only I cannot. The moment I go to the window that is now open for me to exit through, the weapon dissapears from my hands, my hands also go away from view, I am left with HUD but nothing brings back the weapon, I cannot go through the window for some reason. I have stopped, exited, closed the game, opened it back up, shot down the helicopter again, went back through the elevator to the tunnel, anolyzed the tissue only to find as I went to exit the room the same thing happens. I did not have this issue on Veteran, but Post-war Human is where I am having this glitch now. As "Veteran" I was able to play the entire campaign from start to finish with no glitch, but on Post-War Human I have ran into my first one.

Bug.
It worked fine for me though.
Try to re-play whole level maybe?

I know that sometimes things get weird when overclocking and Frank is sitting at 4.8GHz now. I have verified stability with Prime95 and other benchmarking processes to verify stability and everything is fine, but I wonder if it had anything to do with this "glitch". I had played at 4.6GHz through before, but since have upped the OC. I may try the whole level over again thing, but if that does not work, I may try a redcued OC and see if by some weird chance it is affecting the game.

No I dont think it's from overclocking cause I'm having the exact same issue and my system isn't OC.

EDIT: I found that by spamming sprint and running into the gap I was able to get through. It looks like the gun and hands disappear because right after you pass through the window there's a cut scene.