I’m pretty certain I’ve done that.
No matter how far down I go in the folder tree of Reekris-Media, I see inherited RW permissions for Plex from the top level.
I even did bit of poking around with ls -el to see ACL permission and all look correct as far as I can tell (not an expert clearly).
I will add that every time I do the Apply to this folder, sub-folders and files operation, a different single file shows up as having its permissions changed but it never finishes and eventually dissapears.
In a bout of frustration last night I just caved and decided to go with a new Shared Folder.
I expanded Test-Media with folders called Shows and Movies and added them to the Plex Media Directory. Disabled automatic scanning and trash emptying. Then just used File Station to Move To all the files from the old directories to the new ones.
After moving, I had plex manually rescan to see their new locations in under the new Shared Folder. Then I removed the old media locations from Plex Library.
After this I just deleted the old Shared Folder, restarted, stopped Plex, renamed the Test-Media to the original name (for SMB share purposes and laziness), started Plex and added the new media name, manual scan again. Plex located everything successfully again, deleted Test-Media from Plex Directory.
All is right with the world again. Auto scanning, adding, removing all works.
I think whatever process I used to migrate volumes made something somewhere in the DSM system very unhappy.
Thanks for all your assistance through this, I think for now I will consider this fixed as I do not plan on adding more volumes again soon.