multi-layer-relations fail

hi there,

i'm playing around with relations and get this error:
'Cannot replace field: "song_musicians" because it is of not allowed field type: "relation", which can cause loop or other problem'

[problem]
cd-detail-page shows songs, each song shows some fields, but not it's musicians, instead I get above php output per song.

[what works]
- cd-detail-page shows songs, each song with some other simple text fields like 'composer' and 'duration'.
- musicians-category-page successfully shows musicians with theirs songs.

[details]
- I have 3 content types, say "CD", "Songs", "Musicians".
- songs have {n} musicians related. (relation-field "song_musicians")
- musicians have their songs reverse-related (relation-reverse-field "musisician_songs")
- cds have their songs related (relation-field "cd_songs")

[setup]
FC 3.1.1
Joomla! 3.6.4

thanks for unravelling my head