Low fps in this world I created in version 1.0 (especially when I'm near constructions)

I have a world that I created in version 1.0, when updating my mcpe for version 1.2 I entered this world and realized that it is very lag, running at about 5 fps.

This lag did not occur in version 1.1 nor in version 1.0, this horrible lag started in 1.2 beta 1 and is still in beta 2.
The fall of fps is more intense when I am close to my constructions

Samsung galaxy j3
1.5 GB RAM
mcpe 1.2 beta 2

Download world with lag:

https://drive.google.com/file/d/0B1zkPnmTUGpjOWlOV3dLNmw0WjQ/view?usp=drivesdk