Minecraft wiki entry for Development_versions, associated text: MC-128770 – Woodland mansions still generate in dark forest hills.
MC-132306 – Snowy grass without snow near lakes in snowy biome.
MC-133582 – Dolphins try to catch up with boat on land.
MC-137140 – Llamas cannot spawn in shattered savanna plateau.
MC-137956 – Lakes still generate in superflat preset "Overworld" after removing its tag.
MC-138734 – Spawn point for seed 0, world type Buffet with badlands plateau biome is under surface, ⇒ player dies.
MC-138782 – Stranded dolphin tries to catch the boat on the water and stops beating.
MC-138939 – Fish and dolphins spawn in water above sea level.
MC-152966 – Increase in villages generating in versions after 1.10.
MC-169523 – As of 18w06a, the sand, clay and gravel blocks no longer generate around small lakes.
MC-177016 – Some lakes in frozen biomes generate unfrozen.
MC-190724 – Spawning in solid blocks in single biome "Badlands Plateau" world.
MC-197688 – Mountain edge never generates.
MC-200640 – Despite being a coastal biome, mushroom field shores don't have a warm/unique water color.
MC-200803 – Gravelly mountains+/modified gravelly mountains placed incorrectly in the biome selection.
MC-217906 – Large amounts of axolotls cause performance issues.
MC-224494 – Regular dirt can generate naturally on the surface near pools.
MC-225030 – Dungeons are extremely rare compared to in the past.
MC-225506 – Grass blocks can generate naturally in underground pools.
MC-225842 – Flowers can generate on large plants near lakes.
MC-225858 – Seeds and flowers appear in ponds.
MC-226000 – Pointed dripstone items in underground pools.
MC-226437 – Water lakes generating in snowy tundra's can sometimes contain dark spots.
MC-226682 – World can fail to render/load causing visual issues.
MC-227064 – Floating grass can still generate above water lakes.
MC-229365 – Large amounts of goats cause performance issues.
MC-231400 – Modified badlands plateau and mountain edge don't generate and gives out invalid biome data in single biome worlds.
MC-233661 – In some cases, sand blocks generating over lakes do not cause light updates, resulting in large dark spots.
MC-238006 – Emerald ore and infested blocks do not generate in snowy mountain biomes.