I’ve been having this issue and it’s making it impossible to play. It mostly happens when I alt tab but sometimes it happens on its own. Probably started last major update
usually each update optimizes the game for new graphical changes, but same goes for the performance. if the performance drop outweighs the optimization, then you could get a super slight decrease in performance, and usually, that comes with its own cons. if you have a low performance GPU compared to what you are running it on, there is a good chance that when you alt tab back into the game, it overloads your drivers and they tweak for a couple of seconds. this then in change, reduces your game’s textures one step down, until it goes to the lowest and you restart the game. my suggestion would be to set the game on fullscreen window, and use the windows key instead of alt tabbing, since alt tabbing is pretty much one of the main roots of this issue that i used to have, when i ran the game on a 2080 super. upgrading my specs did help, as i boast a 5070 now, and it no longer happens to me, even while running extremely high resolutions.