[Client](?) Game stops after ~25 seconds

After the latest patch, I have been having this issue where I start a game, and after 25-30 seconds, the game disconnects me. I get the telltale signs of it: 500 ping flat, ambient sounds still playing, etc. I have to close the window and reconnect to play the game. I can usually get back in right after the first minion wave spawns, so I'm not missing any gold or xp, but this last game I played froze my computer, I had to restart the whole thing, resulting in me missing half the game, getting a leaver warning and not getting any xp or mission progress. I have done client repairs and the Hextech Repair Tool, nothing has solved this. For about two games that took place a few days ago, the issue seems to have been resolved but now it is back. Any advice on how to fix?