I have a similar crashing issue that appears to be related to the number of Chickens/Cows/villagers are loaded in memory...
when I kill off animals, the issue improves
when I bring more animals back, the issue returns
when I go far enough away from my base that the animals are removed from memory the game stabilizes.
Happens across multiple worlds and across multiple iOS devices.
I would be willing to share the worlds... Where would I send them, and do you have instructions of how to do that on iOS?
I'm having this issue too. I think it started 2 versions ago with the water update. I've got 2 worlds with a bunch of cows/chickens/villagers where it's really bad.
It's fine when I start a new world, but once I start building up an economy, the game becomes unplayable.
it used to be that the app would crash entirely and send me back to the app screen. now it just freezes on a scene indefinitely, all activity stops and the screen ceases responding to touch input.
I also have the issue. iPad mini, iOS 11.0.3, minecraft PE v1.2.9. It appears that the minecraft version auto-updated in the last 2 or 3 days, and the latest version seems to have started the bug.
it happens whether I attempt to move part or all of the stack.
As silly as it sounds, the bug makes the game just short of unplayable.
same issue, both on ipad air 2, and iphone 6+
It also seems to be mob related - issue intensifies as cows, chickens and villagers grow. It started with the aquatics update. I wonder if it's related to the fish in the water.
here are 2 worlds that do this:
https://drive.google.com/open?id=1vEnNRDee3K4pl2oZLK2qYQWdWBjUOV34