A new update is being released to address a few issues with the 1.21.40 release. This update will be rolling to all platforms as they become available, so please allow time for the update to reach you.

Fixes:

Realms

• Fixed issue where game mode and difficulty were not being preserved after uploading or replacing world in Realms Slot. It should now be safe to play Hardcore on Realms, regardless of what kind of world the Hardcore world is replacing.

Technical Updates

Biomes

• Fixed an issue where chunks created before 1.17.40 could behave as Ocean biomes, with ocean-like fog, sky color, and mob spawning (MCPE-186928)