Upgrading a world from before 26.1 can cause data from other worlds to get saved inside it

No closed caption is produced by the sound played when riding a nautilus

Mob spawning checks for biomes incorrectly at biome borders

Standing signs next to blocks now have an extra dark looking face

Debug renderers stop working when changing dimensions

When creating a Water World superflat world, the player spawns at the bottom of the sea

Area effect clouds with duration greater than or equal to 2147483628 disappear after a tick

Players can desync from their mounts when jumping on a happy ghast

Luring mobs onto blocks at Y=-64 will instead make them pathfind to the highest elevation

Player dies by falling from 22.00001 blocks instead of 23 blocks

Fall damage occurs from jumping from 2 blocks up

Chunks on the corner of the rendering distance are not synchronized between client and server for the terrain

Invisible block entities and items disappearing

Crash upon loading chunks when teleporting

Lock field on containers and minecraft:lock data component do not get datafixed correctly when a \ is present

Observers no longer detect redstone dust powering/unpowering

Redstone dust doesn't update properly

The rotation of a wall/ceiling lever and button does not affect the update order of wire in Redstone Experiment

Dropping a stack of items while in the creative mode inventory deletes them

Stepping up blocks while falling on the side of them can sometimes allow players to climb to normally unreachable heights

Naturally generated End Stone drops in cases where the Obsidian platform generates inside the island

Chunks occasionally have large dark areas in the sky

Riding an entity into portals may cause the game to softlock

When you are riding an entity through portals, you and the entity may teleport to the wrong place

Shulkers' models sometimes appear offset upon end city generation

Creepers with potion effects no longer create area effect clouds upon exploding

Attempting to step up while controlling entity and moving fast often glitches

If players have max health over 20 and die, when they respawn they will have 20 health instead of their max health

Soul Speed uses durability in creative mode

Entering the Nether breaks the game

Frost walker no longer works with void or cave air

Entity effect "play_sound" Field "pitch" value upper limit is 1.0 instead of 2.0

Frost walker replaces flowing water now

Trying to generate new chunks crashes the server

Random "Failed to store chunk" error

Crash when randomized_int_state_provider is applied to blocks lacking the property

Custom enchantments don't appear in the creative menu

Upgrading to 1.20.5 leads to the removal of all enchantments if item had the "sweeping" enchantment without namespace

Fireworks shot from Dispensers go much higher than before

Out of memory crash when using a preset with a large layer

Game crash when giving bundle with hide tooltip

The game crashes when attempting to eat lily pads or frogspawn

Comparators require a block update to function properly, and droppers/observers receive false state changes

Magma Cubes spawn even if there's only 2 blocks in height

Slime spawns are incorrect

Pre-1.9 chunks get regenerated seemingly randomly when upgrading

Hopper minecarts with a full block above them no longer search for item entities to pick up

The game freezes and eventually crashes when creating a world with the "spawnChunkRadius" gamerule set to high values

Ender pearls can teleport players in spectator mode

The end portal kills mobs at spawnChunkRadius 0