Seems to lose save points often even if you quit to main.

I'm hoping this is the right place for it but does anyone know why Minecraft PE is not saving my progress at times. My son and I play Minecraft PE me on my HTC One M8 and he has a Kindle Fire and sometimes especially lately our world will revert back after we have done a lot of building and such. I am trying to make sure that I quit to menu every time after we are done playing but it still seems to have that problem. When I play with him it is at home on my home wifi but I also play at work on my work wifi without him if that could be a cause? We have had this happen on many occasions now with multiple scenarios as to where we are when we quit out of the game. For example yesterday I started a new world and we built quite the house as well as mined a bunch of iron and even found a little bit of diamonds, only to quit to main and then the next day have it reset back to before we played on that world yesterday. I am now experimenting with copying the file in the Android Games folder and placing a copy in a different location to revert back hopefully if/when it does it again. Any help would be greatly appreciated!

Thanks,

Jeremy