I noticed that in HM2 if I made a loud noise near guards (like cracking his buddy in the head with a crowbar or doing a melee attack) the nearby guard would 'sometimes' react after the option was disabled.
Usually, but not always, if I save and reload after conking his buddy in the head, the guard would not notice. It might be tied to some in-game metric that reacts if an NPC is taken out of play in some fashion, or some other factor that may cause an alarm or a target lockdown.
Just my observations and thoughts.
No suggestion. There is literally 22 functions or more in this game dealing with AI sensing this or that, plus the cameras, plus likely other things.
I blocked what I could.
Have both 3.1 and latest .NET CORE and FRAMEWORK
.NET Core 3.1 Desktop Runtime x86 Link
.NET Core 3.1 Desktop Runtime x64 Link
.NET Core Current Runtime x86 Link
.NET Core Current Runtime x64 Link
.NET Framework (get latest) Link
(Both of the Net-Core MUST be installed x86 and x64)
and REBOOT THE PC!