It’s been a while since the Iceborn came out for PC, and despite its big success, it’s not perfect. The first major problem was revealed by a large number of players early, and included complaints that matchmaking wasn’t working right and there was a high possibility of losing your saves and characters.
After these complaints started raining, Capcom finally made a decision and promised to fix this problem in the next update. As it turns out, the game save error started in October 2018, when Kulve Taroth was added to the game via a title update, and from there on, the solution was to shut down the game as soon as you receive the message “Failed to read saved date for Monster Hunter World: Icerborne. Create new save data?.”
Now, two months after the problem started, Capcom has released Patch 10.12.01 to address those CPU usage problems and save game errors:
[PC/Steam] Hot fix patch 10.12.01 is now live, related to CPU utilization and Save Data compatibility issues. Please make sure to update to the latest version before your next play session.https://t.co/u7IIf4zvPM— Monster Hunter (@monsterhunter) 17 January 2020
As for the matchmaking problems, it’s most likely an issue with incompatible versions of the game linking up. To put it simply, if you and your friends want to matchup, you all need to be running the same, most-recent version of the game. One person running and outdated version can gum up the works.