Lots of things just disappeared!

So at first the newest update for Minecraft pe 1.12 was working great. Nothing was  disappearing which was my biggest problem with the last update.

But then a few days ago I longed in and my horse I had been riding was gone, all my villagers that I just started to breed again after they disappeared on the last update disappeared again, some sheep and cows gone, and then I realized a hole building was gone and lots of trees just vanished to. 

A lot of my work is gone and it's kind of frustrating. Please fix.