I don't know if my game had a bug or not but in my case if I got killed a couple of times in a place after resurrecting (for 2 or 3 times) the monsters were not where to be seen.
Since I don't like stealth after I realized this I let them kill me!
Try to get killed again and again in the same place without trying stealth and see if you are lucky. I though the game adjust difficulty automatically.
If real is what you can feel, smell, taste and see, then 'real' is simply electrical signals interpreted by your brain
From The Matrix