Is it possible to remobe _afpovertcp._tcp.local from ser name?
Did you try adding the server name and IP to your host files in Mac? I would recommend having a static IP on your NAS for this. 


Launch Terminal, type sudo nano /private/etc/hosts and press Return. 
You’ll need to also enter your admin password to execute it, as with all sudo commands.
You will now have the hosts file open in the Nano editor. Use the arrow keys on your keyboard, to navigate and edit the file.
In your case it can be:

192.168.0.20         Server(type any name that you prefer)

Like with the Windows method above you should just add the desired IP followed by the hostname (or domain name) at the bottom after ::1 localhost.
Press Control-O to save the file.
Flush the cache from the terminal with dscacheutil -flushcache 
Test with the name that you have put.