Hey,
after many of you have experienced fatal error while joining custom maps I have decided to rollback on todays update. The current update will still be available on the BETA-branch of the game.
Rightclick on the game -> Properties -> Betas and then select the beta branch to join.
Otherwise I hope to find the source of that error soon and will re-release the update to the main branch after that. Sorry about the hassle!
Take care,
Jonas