I'm not sure if I understand you well. At the bottom of the smb.conf file there's the "Share Definitions" section with various path settings which I've never changed. They are identical to the default settings, i. e. everything is commented out with the exception of the printer settings. Which path exactly do you want me to check or change?
If you have never changed the paths the problem is not there. I thought there would be sthg missing because when I upgrade most of the times in the configuration file /etc/samba/smb.conf the path lines uncommented at the bottom dissappear.
When samba upgrades, it pops a text window asking to keep the existing configuration or bring a fresh one. If it brings a fresh one, your definitions are gone.
The upgrade process on my computer seems to be different or my client has never received an upgrade. I've never seen such a window during the update sequence, and the smb.conf file still contains the line for the smb min protocol I added a long time ago.