Same Here. Thanks!
I changed the Computer name to match my DNS entry, but I assume you could change the DNS entry to match the computer name on your Domain Controller.
Example:
My Domain Controller computer name was ad01.aruba-lab which did not work because my DNS entry was just ad01.arubalab.net
The Join failed when those 2 did not match. Since this is a lab unit, I change the DC's computer name to just ad01 and it worked.
My thought is that I could have also changed the DNS entry to ad01.aruba-lab.arubalab.net if changing the computer name was not possible. I did not test this though.