To fix it, I just moved the unmounting before the network shutdown in the shutdown list. Here is how:
Change directory to /etc/rc6.d and list it's contents.
cd /etc/rc6.d ls -la
You are looking for S#wpa-ifupdown and S#umountnfs.sh. wpa-ifupdown's # is normally 15, umountnfs.sh's # is normally 31.
So you should see these two amongst your listing:
S15wpa-ifupdown ... S31umountnfs.sh
If these numbers are the same in your case, you can now type:
sudo mv S31umountnfs.sh S14umountnfs.sh
This moves your samba share unmounting to an "earlier" position in the shutdown list which *should* get rid of the annoying hangs in the shutdown process, it cleared my hangs up.