some bugs with the villagers

there are some bugs with the villagers
1. I have a farm of villagers, they spawn normally bat when i go out from the chunk for a lot of time they return 2, the originals.

2. I stayed a lot of times in the farm, and now i can't play with my world because when I enter in the world minecraft crash. I also have tested to transfer the world in the windows 10 edition and also this crash
I have a samsung galaxy s6 and please fix this