add an artist to a playlist double all albumsongs

Hi folks,
I’m new to Volumio (using the primo) and I’m not “in” all features and functions but this seems a bug to me:
when I browse my artists-list and save an artist to a playlist (with all his albums), the albums appear double in my playlist like this:
album1 - title 1-10
album2 - title 1-8
album3 - title 1-15
album1 - title 1-10
album2 - title 1-8
album3 - title 1-15

Hope this is not a feature or a problem with my folderstructure upon the usb-harddisc?