Oh man, I was about to call it quits after another evening of banging my head against the screen. I took a look at this post
#47252
and took another look at my NFS permissions in synology and realized the IP I gave permissions to (supposed to be rune pi) was incorrect, updated it and boom, source shows up. For others working with Synology NAS take a look at NFS permissions:
The Answer: A bad configuration of NFS on my NAS Synology.
For those who have the same problem:
in Control Panel/shared folder/music
In "Permissions", verify if on the line "admin", read/write is checked.
After in "Autorisations NFS"
I have the configuration like this:
Hostname or IP: 192.168.x.xx (it's the ip of my runeaudio)
Privilege: Read/Write
Squash: Mapping all users on admin
Security: sys
And check all after (mode asynchrone...)
While trying to debug I have not been able to ssh into my pi (using root/rune) but that's a battle/post for another day.
Thank you for all the helpful suggestions, it is much appreciated.