Bubzkji complained about the mat_monitorgamma bug
Astralis' sixth player Lukas "Bubzkji" Andersen complained on his Twitter account about a bug with brightness in the game and addressed the developers to fix it.
this mat_monitorgamma bug is so annoying, it's been here for 2+ months. Everytime you tab out and tab back in, it makes your game darker.— Bubzkji (@Bubzkji) March 30, 2021
You have to rewrite a new monitor gamma in console to fix it or have a bind. Pls fix @CSGO ?
I just have a bind for 1.90/91 mat_monitorgamma
Parameter mat_monitorgamma is responsible for image brightness in CS:GO. Users claimed the existence of the bug described by Bubzkji back in 2016 - a relevant complaint was created in the Steam community discussions.
Valve have fixed the bug, that NiP player Fredrik "REZ" Sterner has drawn attention to earlier this month. The Swedish eSports athlete encountered a bug that caused spontaneous mouse sensitivity decrease and forced to restart the game client to return user settings.
Some of the Twitter users suggested adjusting some properties on csgo.exe, however, it could affect game fps settings. To do so you have to uncheck "Disable fullscreen optimizations" in Compatibility on csgo.exe