Warnings are not failures…
The error says that the remote device is write-protected, so you should look on the remote device first.
I’d suggest to use NFS mounts, it’s a bit easier.
To get rid of the warnings, comment the options in /etc/samba/smb.conf.
Note: this file gets restored on boot.
@Tfl the named share on the remote device is set as R/W for everyone, and in fact the PR4100 shows the same message even if I attempt to connect to a non-existent share, so I’m wondering if there’s something a bit deeper going on?