omg... thank you... I have been having playback issues since migration from Unraid Docker to QSV OTiS Plex Linux Ubuntu box. I used rsync to get the app data files. After much troubleshooting and headaches, wiping codecs (sudo rm -r /var/lib/plexmediaserver/Library/'Application Support'/'Plex Media Server'/Codecs) rebooting, all the videos instantly plays back!