Volumio Spotify playlists

Im using Spotify in my volumio and almost everthing works as expected. I can play songs and playlists in spotify without problems. Adding Spotify songs to volumio playlists works as well. But adding Spotify playlists to one of my existing volumio playlists doesn’t work. After adding I get the message that the playlist was added, but when I check the playlist it is still empty.
Any idea?