After saving the game and then joining again mobs from my farms are spawning in random places inside my base, including villagers from a closed farm who end up on the roof where there's no access to it. sheep that I located in a wool farm somehow are back in the minecarts in which they were before moving (minecarts that I destroyed and shouldn't be there).

Killing them doesn't change anything as they respawn straight after joining the realm again, so as replacing the game with a backup. 

Also what is worth to mention this bug doesn't affect my builds. Everything is exactly as I left it, just mobs are all over the place. Downloading a copy of realm and playing locally makes no difference.