Depending on how old that XBian image is, there were changes to Samba in Debian in April that may have caused the issue.
But both OSMC and XBian use upstream (Debian) packages for Samba. So it’s either a configuration issue or the XBian image is using an older version of Samba without the security improvements
It’s the newest Xbian image (XBian_2016.12.23_rpi). I can check the configuration for you (where?), but as I said, Xbian is using Samba 4.2.14. Is OSMC using a newer one?
Use dpkg -l to check package versions
And check your SMB config for differences on the two systems. Some tweaks to the settings may be all that’s needed
OSMC is using the same version.
On Xbian:
ii samba ... 2:4.2.14+dfsg-0+deb8u2 ... armhf ... ii samba-common ... 2:4.2.14+dfsg-0+deb8u2 ... all ... ii samba-common-bin ... 2:4.2.14+dfsg-0+deb8u2 ... armhf ... ii samba-dsdb-modules ... 2:4.2.14+dfsg-0+deb8u2 ... armhf ... ii samba-libs:armhf ... 2:4.2.14+dfsg-0+deb8u2 ... armhf ...
I also copied the smb.conf, but it’s still not working. What else can be the problem?
By the way, this works:
mkdir ~/share
sudo mount -t cifs -o user=guest //192.168.178.21/OTVR ~/share
At the password prompt, I entered nothing. Works perfect. Why not in Kodi?
Kodi uses libsmbclient. You could check that version, but it’s possible it’s the same.
If a command line mount works, use that. Put it in /etc/fstab and you will actually get better performance than if you mounted it via Kodi.
Don’t know why, mounting at the start doesn’t work 
I will give up, I tried the whole day. Thanks for your support, maybe it will work in another version again, I will switch to OpenELEC.
Okay – sorry we could not work it out.
You would be better mounting via fstab anyway, as this will give you better throughput.
I was able to to get Sierra to connect to OSMC’s SMB by forcing it to the SMB1. To do this, Use the Go menu in the Finder and select Connect to Server. Specify CIFS as the protocol and enter the full path of your share. The URL should look something like CIFS://192.168.1.100/Media/ I also noticed that the Finder would sometimes crash if there were too many items at the root directory level.