Hey, idk if anyone already said this but on map 5 "UAC RD-303 LAB", right in the room to the exit door (red doors room), when ya fall on the acid pit on right side the elevator does not work, idk if is intended as the elevator has malfunction or if is a bug, just tought I would let ya know, the image shows which elevator I mean.
Edit: On map 36 "Bone Crunching" found a little texture mistake on these stairs (about previous maps don't know if any secret is bugged so probably someone who tries to gather 100% may have to find any if there is, about exits all of them are achievable for now).
Map 46 "Falling Deeper" also has a texture mistake with a door leaving a huge black gap, left image of the location on map (ignore the fact of me using fly lol, loaded saved file just to not cheat about that).