I’m also having this issue since the Plex app update. I have a 2017 Shield. When I uninstall updates for the Plex media player app on the shield it works fine.
I am going to try the “terminate pause delay to 0”. I had it set to 15 min. Hopefully that works. Get’s annoying having to use some old version of Plex. 
Edit: Setting that to 0 fixed my issue. Thank you!
