I updated from 11.3-U5 to 12.0-U1.
Since then I updated to 12.0-U1.1.
On both 12.0-U1/U1.1 everytime I reboot the server my SMB shares cannot be mounted (any of them). This is not fixed by restarting SMB services. I am not using active directory or anything fancy.
I must go to my SMB user under Accounts/Users and reenter a password. After that everything behaves as expected (until next reboot). This was not an issue on 11.3.