I have added an album to my music library (in the same way that I always do) but the album refuses to import to the library. I can see the folder in the add/rescan dialog directly but the location refuses to appear in the Media Tree and the files refuse to appear in the library. I am super confused. The files are hosted on an Ubuntu server and I confirmed that the folder is set to max open permissions (777).
I have attached a series of images to help explain the problem. I am sure I am doing something really dumb, but don't have this problem with any other files/folders or FLAC files.
View of the shared folder from Explorer:

Location Tree View:

View of the add/rescan dialog showing the folder:

Linux file listing confirming open perms:

Album Artist Library View:

Any and all help super appreciated.