Frozen in Pre-Game Loading Screen

I open the client. I join the queue. I get through Champ Select and into the pre-game loading screen. It gets to 100% and then stays there. I stay locked there for minutes until I Force Quit the game. The ping icon is working fine; the ping is fine. It registers me as In-Game, but it keeps me locked in the pre-game loading screen permanently. In order to play, I have to Force Quit LOL and reconnect entirely. Then, when I can finally see the in-game map, my FPS drops to 0 and I have to wait another minute until I'm able to interact.

It started with the 9.1 patch, very rarely though. But since 9.6, it's been happening every game. The last 3 games have seen me AFK for longer and longer, so I thought it useful to write a bug report.

Laptop: MacBook Pro. Software: macOS Sierra, 10.12.6