I go to The End, go to a return-portal about 2000 blocks away. Setup a Wither trap inside of the portal. The Wither is being killed, and dies from suffocation. Do the same thing again, but this time while the Wither is being killed, the Realm does an auto-backup. When this happens, the Wither will die, but the game will glitch out within a couple minutes, not allowing the player to interact with anything. I will eventually get kicked from the Realm. Once I log back into the Realm, the game is reverted to the backup, and the Wither is no longer trapped and is flying around. This has happened multiple times.