error when copying folders to INTERNAL via Samba share

Hello everybody,

I set up a RasPi (3 B+) with the recent Volumio 2.599. I can access this share, creating files or folders.
When trying to copy folders with sub structures to this share I get permission errors. This happens when mounting the share with Ubuntu 16.04 or WIN7.

I found a workaround turning the share into a public one. In /etc/samba/smb.conf I wrote someting like:

[Internal Storage]
comment = Volumio Internal Music Folder
path = /data/INTERNAL
public = yes
writable = yes
printable = no
guest ok = yes

This does the trick ( … although being a security risk). But unfortunately the smb.conf is overwritten after a reboot.

Is this a bug or is the problem located in front of the keybord? What are the correct owner and group for INTERNAL? I tried volumio (1000) and nobody:nogroup.

Best regards