Monster Hunter: Iceborn DLC is deleting save files for everyone, the game went full of flaws after its Iceborne expansion was released. When players opened the game, they lost their entire save files, and the game started from the beginning. Other problems included 100% CPU Usage, bad performance, lost keybinds, and constant crashes. Capcom came

Source: N4G PC Monster Hunter World: Iceborn latest patch has fixed High CPU usage and Lost Saves.