On both my son's and my xbox one consoles when we play online multiplayer (not realms) or when I'm playing single player, mobs will after a time start to move slowly or freeze in play. Sounds still work so sheep will baah, wolves bark, etc. Sometimes mobs will move, but very slowly, or just a small percent will move slowly while others are frozen. Frozen saddled horses can be mounted, turned in place while you are controlling them, but will not move or jump. A whole town may be frozen while I'm walking through normally or running. I can still trade with frozen villagers. Quit-save-restart temporarily fixes the problem.

As an example: Today took three tamed wolves into a mine. While I was mining they suddenly froze in place. They did not teleport when I moved a good distance from them, however, while mining gravel in a nearby location one wolf died of suffocation. !?! I didn't see the wolf, gravel did not flash red. I headed back to the spot where the wolves had originally frozen. Heard yelping on my way to them. The two remaining were still there and frozen. They accepted food so apparently took damage from something, though their environment didn't change from what I could see. Might have been attacked by another mob. I slept my character nearby, wolves did not join me on the bed. When the next day began wolves were still frozen in the same place. 

I have the disc version rather than a downloaded version for my Xbox One in case that matters. I guessed on the version because I'm not very tech savvy. My Xbox One appears to update automatically so I picked the latest version. Also, I'm using Clarity.

FYI: Unrelated (I think) but weird–villagers are now sleeping in the street even when beds are available nearby, and teleport around when I run through the village. Cats and other mobs also appear to teleport while I run.