Album Artist not showing in music player

I have 2 albums with the same album artist. When I load them in MP3TAGS all 21 tracks of the 2 albums are correctly showing the same artist and album artist. However one album is not showing correctly in apps like DSAUDIO or MConnect. When I display the album in MConnect by folder the album artist is missing. I also checked the metadata with Musicbrainz Picard but also there all fields are showing correctly. Any ideas what could be the cause and what I could try to correct it?
Thanks!

I think the easiest way would be to compare a file that works with one that does not.
All the field names should be identical (and not e.g. one ALBUMARTIST and one ALBUM ARTIST). Also, all files should have the same tags (V1, V2 etc and preferably no APE).

the 2 albums of the same artist have the same ARTIST, ALBUMARTIST, GENRE etc. tags with exactly the same values. can't detect any difference between the albums, also tried kid3.

for some reason the problem album shows the directory name as ALBUM name, whatever I put as ALBUM name.

must have been something strange in the flac source files, I converted the flacs to wav and then back to flac and the problem is solved.