It is more than just that one sound though. It is all those sounds I listed, plus others before it that I didn't take the time to document.
Since it seems you aren't grasping it fully yet, I put even more time into this than I should have to. I decompiled the rpa files and followed the script until those scenes. I know exactly nothing about renpy, but I am pretty good about intuiting stuff. In your defense, I see nothing blatant that would cause it to act the way it is, but something is clearly doing it (spoilers, there is).
For example, the first noise, Geralt kicking the door in, is executed via this code:
Code:
play ambient4 "audio/day2/door4.mp3" volume 2.0
I can easily see that is supposed to be controlled by the ambient4 slider, with a default volume of 2.0 (whatever that equates to).
Similarly, the sword "shing" noise when you wake up is this code:
Code:
play ambient4 "audio/day2/sword.mp3" volume 27.0
I'm not sure why this one is 27.0, as that seems massively, earthshatteringly louder than 2.0, if the volume sliders actually affected them. But, they are both the same volume for me (the excessively loud variant).
The MGS sound is alert.mp3. Where she opens the door and it plays twice in a row the code is:
Code:
play ambient5 "audio/day1/alert.mp3" volume 2.0
play ambient5 "audio/day1/alert.mp3" volume 3.0
So, after spending way more time than I should have had to in order to track all this shit down for you, do you want to know why none of these sounds are controlled by the sliders, which you swear up and down multiple times to the point of dismissing anyone that mentions it work perfectly?
Of course I had to comb through this crap line by line because I had no idea that you defined 5 new channels and randomly tossed various sounds into them without any consistency, but you'd think that the person that wrote the code might notice the settings and think, huh, I know I made 5 of those, why are there only 3 showing up?
Jesus Christ, I shouldn't have had to debug your code for you. You're welcome.