So... Just encountered this.
I queued up for a ranked game, everything was normal in champ select, and my internet is 5 bars. The game starts to load, but I notice that I haven't gone to the loading screen. I try restarting the game since I kinda need to load into the game, but I get a critical error when I try to log in. I manage to log in after another try, click reconnect, and once again am hit with a critical error. This kept going on over, and over, and over again, even when I went into my task manager and force shutdown anything related to league. I only was able to get back on once the game had been remade, but now I'm sitting here with a remake from a game I physically couldn't connect to, even with 5 bars.
I better not get a ban because I had critical errors from starting up a game in the exact same way I have for countless others.