[beedaddy]

Hmm, so I always need ALBUMARTISTS, which consists exactly of the names from ALBUMARTIST, seperated by "/"?

When there are multiple album artists, and the names are not separated by artists separators (since "," is sometimes part of a name and sometimes not Kodi can not assume it is a separator) then yes. Historically the separator is space-slash-space by default, but you can tell Kodi to use a variety of different separators for artists including ";", or " feat. " etc.

Just as a side note: I'm in the process of adding the ALBUMARTISTS tag. In some cases, this does not help. In my despair I then removed the MUSICBRAINZ tags and then it worked. This surprised me (since I set the provider for album information to "Local information only").