This has been happening to me for months. I finally decided to report it as a bug in the Android TV beta forum in the hope that it gets more visibility by Plex devs.
Plex for Android 8.1.0.17650-beta
When I finish watching something on the Shield via Plex and return to the Shield home screen, a notification appears saying the content is still playing, giving me the option of continuing or stopping. This notification only appears if I let Plex play the content completely, and then return to that content’s pre-play screen. I can prevent the notification by ending the Plex play session before it gets to the end of the content (e.g., while a movie or show credi…