League/TFT don't launch & computer grinds to a halt (100% CPU)

Recently I've had an issue where games of TFT don't start (also tried with League practice tool and got the same issue). I am able to successfully queue, the queue pops, and the client disappears but the game itself doesn't launch and my computer grinds to a near-halt. Every function of the computer takes ages to respond and the only way to fix it is by going into task manager and ending the league task. The task manager shows CPU usage at 100%, but this is IMMEDIATELY fixed the second I close the instance of the game that is trying to start.

I've tried repairing and reinstalling, but neither have helped. I've played many games on this computer before but now 100% of my games on this computer experience this problem.

I'm running Windows 10 on a computer with a Ryzen 3700X and 2070 Super, so the problem almost certainly isn't with my specs.

I've not had this issue with any other games and the League client runs perfectly fine.

I'd love a fix for this at it makes the game literally unplayable.