Duplication of an item removed from a chest when turning off and on your Android device:

1. Open the chest
2. Take the item you want inside the chest
3. (Try crashing the game if the step below this is not working)
4. Switch off and switch on your phone (without quit the world)
5. When the minecraft window appears before the lock screen, switch your device off and on again (cause the low ram and closed the lockscreen)
6. If the lock screen appears without lag, unlock your screen (minecraft pe will closed automatically)
7. Open your minecraft pe
8. Open your world
9. Then your item was duplicated

It appears that the inventory item was saved but the whole world was not saved (your item will keep in your inventory but your item that was taken from the chest is still exist), it will happen if the system closed the application for some reasons or crash in-game, (sometimes) When you put the item back into the same chest (with the duplicated item) then reload the world, the original item and the duplicated item are gone. (Not only chests)