In particular this endpoint, for the MBID bd01c9d7-89dd-4cb4-9baa-a43bfa292bed at index 54
 
https://api.listenbrainz.org/1/popularity/top-recordings-for-artist?artist_mbid=bd01c9d7-89dd-4cb4-9...
 
Returns a single recording with these values:
 
Object {"artist_mbids":null,"artist_name":null,"artists":[],"caa_id":null,"caa_release_mbid":null,"length":null,"recording_mbid":null,"recording_name":null,"release_color":{},"release_mbid":null,"release_name":null,"total_listen_count":620,"total_user_count":209}
 
 
Per the #metabrainz IRC chat, these should be filtered and it's a bug.