Certain Folders in NAS Missing From "Artists" and "Albums" Views in BluOS App

Hello, Bluesound support crew!

Recently, I have noticed that a few folders in my NAS, a Linux server running the Samba Windows-like file sharing service, do not appear in the BluOS app under "Artists" or "Albums".

Connectivity to the NAS is good, and all other artist and album directories appear properly in the BluOS app. When I look for these folders in the BluOS app, under the "Folders" or "Songs"  browsing options (which basically appears to be a CIFS/SMB browser), I can see them there, and I can even play music on my Bluesound / NAD system that is stored in these folders from these "Folders" or "Songs" views in the BluOS app. Similarly, I can access and play music from the folders in question when I browse them from my laptop computer using the same access credentials. So, given that my computer and the BluOS app can both access and play music in these directories and files, I am quite sure no permission issue exists with them. I also manually verified the permissions, and I see that they are the same as files that do properly appear in the BluOS index.

Among several troubleshooting steps, I have tried the "Reindex music collection" and "Rebuild index" tasks in the BluOS app, to no avail. I also tried renaming the folders in question to simple names with no spaces or punctuation, and I even moved some song files from these folders to folders containing music that does appear in the Artists and Albums folders, but those tracks still do not appear in those views in the BluOS app, even after a re-index. Curiously, we recently copied a number of songs from various folders to a new folder to make a sort of playlist -- this folder is also not in the "Artists" or "Albums" views, but the originals are.  O_o

A number of recently imported albums do appear properly in all views. So, it is not that all new music is not accessible from all views; only a few artist folders do not appear in all views.

I have tested this from the BluOS app on three different iOS devices on my network with the same results. We only noticed this problem relatively recently, while we have been happily running BluOS playing music from our file server for some years now without issue.

BluOS version: 4.6.3

iOS app version: 4.6.2

To summarize the problem: some folders / directories in my NAS do not appear in the "Artists" or "Albums" views in the BluOS app, though they are available in the "Folders" and "Songs" views of the BluOS app. I would like all my music to be available from the "Artists" and "Albums" views.

Thank you for your help! If you would like any more information about this issue in order to advise on how to solve it, please let me know.

Micki