I came across this problem this weekend when I had to factory reset my Shield TV… The iOS and Android player apps that have synced content don’t seem to let you delete that synced content if the server is no longer linked to your account. I can go in and “delete synced content” but it doesn’t wipe the content synced from the deleted server. I ended up just (iOS) deleting the app/resintalling, and (Android) wiping the data of the app/re-setting it up. I’m sure this generally much of a problem because people don’t delete servers very often, but since the Shield TV has many issues with Plex… might be worth fixing for us who have to factory reset any time plex decides to use of the entire internal 16GB partition (even when adoptable storage has expanded it well beyond that limit).