I have checked the permissions on the NAS and as far as I can tell from the settings, all the shares are setup identically. All the disks (16 in total) are formatted as reiserfs and are identical to each other. Once imported, MC20 can play and delete files without issues. It is just the importing part that does not happen automatically.
Coming back to the basics, how does MC20 update the existence of new files on a network share? If this is the root of the issue, maybe I can ask in the Unraid forums to see how I can check this manually.
Is there a way that I can setup a link for manual refresh of the auto-import in the theaterview mode?
Do you have any problems playing or accessing files in that directory? I've seen similar issues when filesystem permissions were not set correctly for one folder (but were set correctly for other folders).
Are all of your disks using the same filesystem? Is is it possible one of them is formatted in a file system that doesn't report events and the folder is located on that disk, etc. etc?