Have found that name tagged horses with saddles and armor despawn from the world. Axolotl that have been bucketed and even named tagged all despawn. Tamed/penned sheep chickens and pigs are also despawning. This has been happening since areas to house animals have been built in this realm.

Example, had several sheep dyed different colors. Had 4 pink, 2 red, 2 green, 2 blue and 2 orange, and a couple white. logged off my realm that only 5 people have access to, that I trust, 1 was logged in and in the nether. 2 pink, 1 green and a white were present when I logged back in 20 hours later.