After updating Plex Media Server App for Seagate Personal Cloud to version 0.9.12.11.1406-8403350, the App Manager console screen now displays the message "Automatic startup has been disabled for this app. Confirm that the app is compatible with the device's firmware".
As a result the Plex Media Server no longer auto-restarts after a power failure (which causes a restart of the Seagate NAS).
Help !!!