Let’s get to the bottom of it.
There are quite a bunch of hostnames that macOS is using.
hostname is just one of them.
For example, look what’s reported on my machine:
alex@alexmbp ~ % scutil --get HostName
HostName: not set
alex@alexmbp ~ % scutil --get LocalHostName
alex@alexmbp ~ % scutil --get ComputerName
alex@alexmbp ~ % hostname
See what happened here? my Mac has at least three hostnames here: especially interesting is local hostname – note
-3 suffix? That’s because I had a bunch of my older MacBooks pros, named the same, still powered, sitting around.
I’m not sure which of those hostnames is duplicacy using but if it is “LocalHostName” – then this would explain your issues.
Check what do you see on your machine, then you can force all the hostnames to the same something using
--set instead of