I have also seen the same "clustering" behavior in my pens, but for me on a Realm, in the same world were animals then later disappeared.
I've also seen villagers going insane with an entire village trying to go into and out of the same house/door. Not sure if it's a related behavior.
This is only an issue when playing on a realm for my wife and I. We can work around it by setting the GUI to classic and make the map zoomed in a crafting table. I read somewhere that the issue is from the realm servers running Windows 10 version which does not have the anvil recipe for map zooming.
I could have sworn I found that information here, but don't see the comment any more.
Experience this in 1.0.3 on a realm. I use a nexus 10. Seems to happen when I travel away from my farm and the chunk unloads. Doesn't happen on save and reload. Happen on both peaceful and easy. But the biggest loss was on Easy.
Confirming that this is still present in PE1.0.2 using a Nexus 10 and Samsun Tab 4, on a Realm server.
On version 14.3 my wife and I both experience this issue. If I host, she has it. If she hosts, I have it. I am on a Nexus 10, she is on iPad 2.
Also, Safari Explorers on Android version of Bedrock. (My son is quite upset)
Same steps to reproduce, but cannot access the files to check the version mismatch.