Minecraft wiki entry for Development_versions, associated text: MC-236756 – Biome-exclusive mob spawn rates are reduced.
MC-236858 – Seeds that spawn you in the middle of the ocean cause lag.
MC-237275 – Game crashed when creating a single biome world with a custom biome / java.lang.NullPointerException: Cannot invoke "bze.a()" because the return value of "bzg.a(int, int, int)" is null.
MC-238049 – Passive mobs (cows, pigs, sheep, chickens) sometimes do not spawn.
MC-238076 – UpgradeData in chunk is not migrated to new world height.
MC-238375 – Crash and/or data corruption upon attempting to save a world with a world border center over 30 million blocks.
MC-238587 – Sprinting while flying into a block causes the screen to rapidly zoom in and out.
MC-239423 – Kumi Tanioka isn't under "Music composed by" in the credits.
MC-239856 – Upgrading old worlds causes vines to have the wrong block state.
MC-239857 – Fences, iron bars, and glass panes often use an incorrect block state after conversion.
MC-239884 – Water from old chunks don't properly propagate into new chunks.
MC-239899 – Connected redstone does not properly upgrade from older versions.
MC-239994 – Old worlds with non-bedrock blocks at 0,0,0 do not upgrade chunk column from 0,0,0 to 0,-64,0.
MC-240030 – Infdev and Alpha holes in the world below Y=0 after conversion since 21w43a.
MC-240494 – Duplicated mineshafts with new cave generation.
MC-240507 – Mob Spawning in structures fails in pre-1.18 generated monuments/swamp huts/outposts.
MC-240570 – Biomes in old chunks are not copied to new caves below Y=0 when chunks are extended.
MC-240610 – "Allow Server Listings" option doesn't save its last setting.
MC-240783 – Powder snow does not reduce or negate fall damage.
MC-241111 – Some Mojang employees are not mentioned in the credits.