Entities in the Realm lose visibility randomly. This has effected hopper mine carts, including named hopper mine carts, tames animals such as horses and beds. If they can be located, as in the case of beds which occupy a fixed position in the world,, they can broken and will return to the players inventory. In some case, such as mine carts and horses, these entities cannot be found and may become embedded in walls.

See attached image of the selected bounding box of an invisible bed.