When going to a different app in MC:PE the screen glitches

A friend mentioned this bug so I decided to report it. Whenever my friend is leaving a server and goes to a different app the screen turns into this back in the game: 

He also mentioned how this happens 75% of the time on servers and 50% of the time on local worlds. We tried to reproduce on Windows 10 and it did not happen but every mobile device it did.