Music player error (NFS on NAS)

i use OSMc on RPI2 with a Synology NAS. Video player works fine (using NFS), but i’ve got an error using music player. I choose a song, it stats, after 5 seconds it crash.
Outputs logs are :

15:39:59 713937.875000 T:1582298096 ERROR: COMXImageFile::ReadFile nfs:// in the Deep/cover.jpg not found
15:39:59 713937.875000 T:1582298096 ERROR: Previous line repeats 1 times.
15:39:59 713937.875000 T:1582298096 NOTICE: LoadJpeg: unable to load nfs:// in the Deep/cover.jpg
15:40:02 713941.562500 T:1546646512 NOTICE: [Artist Slideshow] script version 2.0.0 started
15:40:02 713941.562500 T:1546646512 NOTICE: [Artist Slideshow] debug logging set to false
Any idea ? how can i debug that ?

File cover.jpg exists. On NAS :

$ ls -alFrt /volume1/music/Adele/Rolling\ in\ the\ Deep/cover.jpg
-rw-rw---- 1 nicolas users 27139 Mar 24 2015 /volume1/music/Adele/Rolling in the Deep/cover.jpg

All logs :