Tablet - Android - Samsung Galaxy Tab 4 Nook
The bug is that when you enter a world (call this state a) and play for any period of time so that you leave the world (call this state b) it is different in any way other that waiting for the quit to title button to return you to the title(or not pushing it at all)(Other ways including putting device to sleep, having to close the game ect.) When you return to the world you will end up inthe same location as state b but the world will be in state a. In other words it is like the playing between a and b never happened and the new things are forgotten. A common thing that I have had happen to me is on both worlds this has happened to me on there has been some degree of active redstone circuits.
This has also been to be the case with some other players.
What I expect would happen is the world to revert back to sometime right before state b instead of all the way back to state a.
Some other devices this has occurred with are:
Droid turbo running lollipop
ASUS MeMo Pad 7 176cx
Samsung Galaxy S5 running Android 5.1.1
Samsung Galaxy S4 running Android 5.0.1