We've released a mandatory update to TF2. The notes for the update are below.
Team Fortress 2- Fixed matchmaking sending players to out-of-date servers
- Fixed the server browser showing an incorrect player count in MvM games
- Fixed a crash that could occur on map change if another player was being healed by the dispenser or payload cart
- Fixed a rare server crash when firing hitscan weapons
- Fixed MvM intro video not playing on some Macs
- Fixed the sound precache string table being nearly full in non-MvM games
- This was causing the "error writing string table baseline" and "failed reading message net_SetConVar" errors