Okay, so I been messing around with this bug, you open the chat window, press off the screen when keyboard is up and then your screen goes blue, there's a fix that the client can do which is "Menu>Options>Back" but this lowers draw distance and causes you to place blocks in hand when you hit the fly button, I know it's not just my operating system as it's happened to both iOS and android users, the world this bug is a big problem on is "TheMazeRunner" Hope this helps.