It's been a while and after some searching, trial and error I figured what caused the Windows 7 automatic updates to disable. It indeed has to do with Avast Antivirus and more specifically the "Game mode" function (Settings -> Components -> Game mode). I turned it off a few days ago and never after that has the automatic updates been disabled while running a game. I guess it has to do with Avast, Game mode ON, trying to block Windows updates happening during gameplay (the ones where the countdown begins and the computer restarts itself unless you postpone it manually). Disabling it, everything has been working as before the most recent big update. I guess the feature is pretty cool in itself but I'd like it to actually switch the automatic updates back ON after the game is exited. Otherwise, it's a bit of unneeded feature if it doesn't work properly.