Minecraft wiki entry for Development_versions, associated text: MC-81659 – Fireball and witherskull hitboxes are frequently invisible for some seconds.
MC-104900 – Skeletons, illusioners and piglins with crossbows have broken agility reaction when hit or walking on certain blocks when provoked.
MC-104949 – Mobs cannot jump shorter than half of the blocks.
MC-128247 – Dolphins can jump way too far causing them to hit on land.
MC-134900 – server.properties generator-settings for level-type FLAT not implemented; property is stored in ignored flat_world_options NBT.
MC-145140 – Fireballs cannot be interacted with when summoned.
MC-146928 – Cannot place doors, rails, buttons, pressure plate, redstone, etc. on soul sand.
MC-148935 – Zombies with no AI still convert into drowned.
MC-170836 – Cannot set the top of soul sand on fire.
MC-173732 – Fire and soul fire do not have loot tables