Some items are not adjusted properly if the player sneaks. This seems to affect all "flat" items, but affects carpets and slabs as well. Full blocks are not affected.
MC-163797 Honey Bottle Is Not In Hand When Sneaking
MC-46579 Items are too high up on the arm in 3rd person mode while sneaking
MC-162374 Trident position is not adjusted properly if the player is sneaking