I am also experiencing this issue on Win 10 version 1.1.0. As with others, mobs were previously stuck in the NW corner of fenced areas, but after the update they are getting stuck in all corners. We've had it happen with chickens and rabbits.
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I'm also having this issue.
It may be related/an extension of this problem, but occasionally when mounting a donkey, the donkey dies. I've been playing in multiplayer, and have lost five donkeys in the past two days. We've had to stop playing because it happens most often to one player in particular, and is traumatizing for her.