You could try making a ~/.kodi/userdata/mediasources.xml
file containing…
<mediasources>
<network>
<location id="0">smb://192.168.1.220/</location>
</network>
</mediasources>
and then check ~/.kodi/userdata/passwords.xml
and make sure it has the correct login information for…
<passwords>
<path>
<from pathversion="1">smb://192.168.1.220/</from>
<to pathversion="1">smb://username:password@192.168.1.220</to>
</path>
</passwords>
Rebooting to take effect. I had issues with setting the artist information folder to a network location without this. Alternatively you could just make a system mount for your backup location and point to that instead.