The majority of failures in a SMB network are related to name resolution errors. The solution is to set your Unraid server to a static ip (such as 192.168.1.100) and when you map the drives in a windows explorer window type in \\192.168.1.100 - it should as you for authentication. Type in your username & password, click 'remember'.
Once it opens you can right click on the share and 'map network drive' assign it to a local drive letter and it's mapped.
Now if you're on a domain, or are using a WinS server you can avoid having to it statically, but seriously how many home users are going to have a domain/wins server?
Sometimes windows gets stupid and forgets the mapping - you will then have to right click on the drive in 'my computer' and 'remove drive' ... and remap it after a reboot.
SMB is pretty good - it's just it's craptastic nameresolution that sucks. Go static IP no more problems.
*** edit
Now if you want to be smooth, just edit the c:\windows\system32\drivers\etc\hosts .... add in your server and name, it blammo name resolution works for every windows/linux pc you fix the hosts on .... little more of a pita on a firestick tho.