Unable to join the domain?

Today I set about installing a new server to replace an old one. This was going to be a Virtual Server on our Hyper-V cluster.

I have built enough servers of varying OS versions on Hyper-V enough times to not even think about what I am doing so was a tad surprised when it failed to join the domain.
A quick check of everything showed nothing obvious, as sometime I do make the odd stupid mistake!
The server had a DHCP IP address, I could ping IPs on the network, I was able to download files from the internet – which were about all I normally do before joining a new server onto the domain.
I let the server update itself with the latest OS updates and reboot, but that made no difference.
I then set about checking out the NetSetup.log and work through any issues in there.
After checking that and getting nowhere and starting to lose interest I decided to move the VM to a different node and try and add it to the domain again. This time it worked!

I really have no idea what that is as I have not had that issue before and have joined servers on to the domain with not issues plenty of times.
Maybe if I have a lull in work I will revisit, but as I have looooaads to do I don’t think that will happen anytime soon.