I have same problem, which a submitted a report for the beta. Now its live the issue is not as bad but still there and worse then it was pre 0.15
Any entity that is pushed up close to a block/fence when chunk is reloaded they are pushed out of enclosure.
This issue is making any automatic farms very hard to manage. Each time I load the world I have to spend a fair amount of time putting cows, chickens and villagers back. Also 2 high entities if in a 2 high air space with a block on top will move nearly every time the chunk is loaded.
To add, mobs seem to move to open areas. They don't seem to move to areas that are covered / inside.
Also to add. This is not the old bug of 1 or 2 mobs moving on load this is all of them. ie I had about 20 villagers in the pocket and all of them had moved.
Just updated to 0.15.1.2 and mcpe will not load. Black screen and then android error.
Samsung Gt-p5210
Android 4.4.2
Was working fine before update.