This has got to come down to tagging - although the fact Asset still shows Fleetwood Mac adds uncertainty to the situation - did you try to access AssetUPnP from another control point, as this would at least remove the Naim app as a potential source of the problem.
I assume if you're browsing 'Additional > Album Artist/Album' then we're only dealing with AlbumArtist & AlbumArtistSort anyway, so the other artist values
shouldn't affect it.
In General Settings, untick 'Combine Duplicate & Similar Artists' as it may be masking a funky character problem.
The only other thing I'd suggest is to check for conflicting values (one to many relationship) in AlbumArtist and AlbumArtistSort (and maybe Artist whilst you're at it). The easiest way I know how to do this is by running some SQL within foobar2000. I talked someone through using this a few days ago (they wanted to add the tag album_duration to all their tags) without problem, so I'll copy the instructions here, although I don't think I'll be able to include links as they seem to need manual approval and take a while.
Grab the latest 'foobar2000 download' and 'foo_sqlite component' (just google both terms).
- Run foobar2000_v1.6.10.exe, choose 'Custom', choose 'Portable installation' and select a path.
- Allow the installer to 'Run foobar2000' and pick the 'Album List + Properties (tabbed)' layout with whatever colour you want.
- Select the menu item 'File > Preferences > Media Library' and specify the path of your test music.
- Whilst still in the Preferences window, click 'Components > Install' and select the downloaded foo_sqlite.fb2k-component.
- Click 'Apply', then OK to restart, and foobar should scan your library and display the contents on the left hand side.
- Once it's finished scanning, select 'Library > SQLite console' and a popup window should appear.
Copy the following code into the window and Execute it.
Code:
select "album artist"
from mediaLibrary
group by "album artist"
having count(distinct albumartistsort) > 1;
If there are any values of AlbumArtist that have multiple AlbumArtistSorts they will be displayed.
At this point you could check for consistency across AlbumArtist and Artist by running:
Code:
with distinctArtists as (
select artist,
artistsort
from mediaLibrary
union
select "album artist",
albumartistsort
from mediaLibrary
)
select a.artist,
a.artistsort
from distinctArtists a
inner join
(
select artist
from distinctArtists
group by artist
having count(distinct artistsort) > 1
) b on (a.artist = b.artist);
This assumes you're on Windows of course!