Synology: DSM 7 Installation Archive -- Archived from main thread

Supplemental

chown: changing ownership of '/volume1/Plex/Library/Application Support/Plex Media Server/Cache/fontconfig': Operation not permitted

This error confirms you missed a step in the Permissions changes to allow “Full Control”

After Uninstall + Erase, With all your metadata still in the Plex shared folder
Perform these steps.

@Tyrios

We might have to do a custom migration depending on how badly it is broken – in order to bring the two pieces back together,