AI / Sound glitch

[Resuto]

I tried to play through Penumbra: Black Plague today, and noticed something a bit odd. Once I got to the freezer and an AI appeared, the music changed to combat music and would not change back throughout the game. I did not pay this much mind until I also noticed that later on when you actually physically encounter the first AI, he would not behave like he should, he was stuck where he spawns in and would not move from that location unless he heard a noise. If he did hear a noise, he would then go to that location and then just stand there forever. I thought this might be a glitch so I logged out of the game and tried verifying my steam files for Black Plague. It said that 96 files failed to validate and would be reacquired. So I thought hmm, maybe this fixed it. I started an entire new game and it still would behave the same way. I tried changing graphical settings, sound, using default settings. Nothing I do seems to fix whatever problem this is. I thought it perhaps might be a specific problem to my one machine, so I tried it on my other linux machine and i had the same exact problem. It have 96 files that failed to validate. I am quite stumped on this one. Any help would be appreciated!