This is because there isn't meant to be an actual, playable level above 100. This is true across all s8 games though the actual level varies according to the game (50 in CS, 99 in BS/RS, etc.).
Any player that reaches enough XP to go above 100 will experience this exact issue where the game becomes unplayable. They will have to open a
Support Ticket with the team who will then be able to access their account and lower their XP so they're able to continue playing their game.
When this has happened in the past and the team sees that many players are close to reaching the meant-to-be-unattainable next level, they readjust the required XP to make it exponentially higher. This will prevent this bug from happening in the future and stopping others from suffering this same issue.