13 FPS in-game lock

After latest patch 6.22 I get 13 fps after couple of minutes in game. I used new and old client, lowered graphics, turned off all unnecessary programs, restarted PC, closed clients while in game, but nothing helped. Before this happened I had steady 60 FPS with V-sync on, without it around 100-120. Now first few minutes it's 58-60, and then suddenly drops to 13. I basically become handicapped, I can't see skillshots, can't lasthit, cant even click on stuff. I haven't yet tried to reinstall the game because I want to see if there is alternative way of fixing it.
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