game randomly tabbing out, then fps drops?

so when i'm in game, sometimes it'll just randomly tab out (minimize) and when i pull it back up (praying i didn't die) it will have random FPS drops. these drops tend to happen in team fights or when there's lots of action, which i'd expect to drop FPS but i don't encounter them until this random tab out bug happens.. usually my computer runs league perfectly fine as far as FPS and Ping are concerned... it doesn't happen every game, but it had been happening at least twice a day.. everytime it happens i always restart my client after the game is over.. i submitted a bug report, but was wondering if anyone has dealt with this?