"Playback has stopped because the connection to the Plex Media Server has been lost"

Can you confirm this is your sample; https://drive.google.com/file/d/18JZ945qdP9xwEXrGmFSlOnjyCzAx1JC1/view

What device do you see problems with this video on and if you use a different device, does it play okay? If you are able to test 2 devices and have 1 problematic and 1 working, if you could grab the Plex for Android logs from both it would be a big help!