I use Plex to watch TV/Movies (which stream from my home network) and I AirPlay it to my Apple TV. When AirPlaying, I have no problem navigating away to check my messages, etc.
However when I open some apps, usually games such as Pokemon Go (I like to wait for Pokemon while watching casual shows), it disconnects the AirPlay. Seconds later I hear my show playing through my phone speakers and I have to navigate to the Plex app to stop it.
Why does this happen and how can I prevent AirPlay from disconnecting?