Lag spike while loading player head textures / player skins End crystals placed on exit portals generated before 1.9 do not respawn the ender dragon Credits background jitters Structure block data length limited to 12 Intersecting structures can create corrupted block entities (spawner / chest) Shifting around servers in the server list crashes the game ( ArrayIndexOutOfBoundsException) Leaves change to stone near Lava Pool (Recurrence of MC-48340) End Portal Frames change to Stone near Lava Pool Angering passive mobs in new nether chunks very far away from previously generated chunks, then entering a nether portal causes server to completely freeze Setting the weight in Template Pool to high values will lag world and can cause out of memory error.