Go back to Control Panel - Shared Folder - photo .
Reapply the permissions there (which is at the top of the shared folder)
DSM is giving you problems because permissions are inherited by default.
When you set them manually, it is temporary.
If you have Synology Photo Station installed, it will always overwrite the permissions
(DSM Photo Station owns the default photo shared folder)
– Your option is to:
- Create a temporary holding shared folder (Photo-temp)
- Move your /photo/* → /Photo-temp
- After empty, delete the /photo shared folder
- Rename /Photo-temp → /Photo
- Apply permissions
- Update Plex
