Getting disconnected a few seconds after joining the game

[rfxDarth]

Pretty much, subject. This happens on both custom and vanilla clients, W16.1 and W16. It used to only happen on one of the Russian IP's which I used to blame sanctions/censorship for, but now I'm facing this same issue in another location where there aren't any such restriction. Another ISP in here works just fine. Looking under the hood, it looks like the game server just sends MSG_CLOSE for seemingly no reason few seconds into the game.