invalid absolute song path from remote mpd / NFS mount


I’m having trouble getting a NAS with mpd (for database serving) to work with Volumio on Cubox-i.

After modifying /volumio/app/plugins/music_service/mpd/mpd.conf.tmpl to include the database reference (and remove the db_file) to contact my remote mpd, at least it acquires the file listing.
It also seems I had to modify the local music_directory in the mpd.conf template to refer to the full NFS mounted music root, in my case: /var/lib/mpd/music/NAS/mp3@microserv (where apparently the mount is symlinked if I add the NFS-share as a drive with alias mp3@microserv.
So far so good.

Now I can browse my collection, but if I press play, I see the following in the Volumio log:

2017-12-21T22:08:24.473Z - info: ADDING THIS ITEM TO QUEUE: {"uri":"music-library/Big Wreck/Ghosts (2014)/03 - Ghosts.mp3","title":"Ghosts","service":"mpd"} 2017-12-21T22:08:24.475Z - info: Exploding uri music-library/Big Wreck/Ghosts (2014)/03 - Ghosts.mp3 in service mpd 2017-12-21T22:08:24.478Z - info: ----------------------------/mnt/Big Wreck/Ghosts (2014)/03 - Ghosts.mp3
which obviously is the wrong path, since it must be

/mnt/NAS/mp3@microserv/Big Wreck/Ghosts (2014)/03 - Ghosts.mp3

(or via the automatic symlink):

/var/lib/mpd/music/NAS/mp3@microserv/Big Wreck/Ghosts (2014)/03 - Ghosts.mp3

How to solve this?