My Mac mini's computer name keeps changing when it resumes from sleep
I've seen this happen when the local DNS server has DNS caching enabled, but doesn't flush the cache often enough (or at all).

You can set your Host Name/Computer Name to a static value using scutil in Terminal. This means that your Mac will no longer change it's name automatically, so it's important that there are no other machines on your network that actually have that hostname. When you run this, replace "new_hostname" with your desired hostname:

sudo scutil --set HostName new_hostname

sudo scutil --set LocalHostName new_hostname

sudo scutil --set ComputerName new_hostname


You can check to make sure the values are set by running:

scutil --get HostName 

scutil --get LocalHostName 

scutil --get ComputerName 


Sources: man scutil

https://developer.apple.com/library/mac/documentation/Darwin/Reference/Manpages/man8/scutil.8.html

http://osxdaily.com/2010/09/06/change-your-mac-hostname-via-terminal/