Windows Server promote to Domain Controller succeeded and failed?

Edit: Ignore this post. It turns out I'm having other problems, even with another brand new install of Windows Server 2012 R2 on a different physical box. So I'm pretty sure there is a different underlying issue. I created a new post with the new info here: Cannot promote Windows Server 2012 R2 to Domain Controller at a new site. "The wizard cannot gain access to the list of domains in the forest."

I just installed a brand new Windows Server 2012 R2 machine.

After doing the basic initial setup (via Server Manager) and installing all available updates, I added three Server roles:

Active Directory Domain Services
DHCP Server
DNS Server

After installing the AD Domain role, the notification appeared that I had to Promote the server to Domain Controller, which I did.

At the end of the Promotion wizard, it said that the Promotion was successful.

Weird thing that I noticed later after a reboot, however: the notification that I had to Promote the server to Domain Controller was still appearing in Server Manager. I tried to do the process again just to be sure, but it would just hang on the first step.

So to be sure everything was fine, I decided to remove the AD Domain role and try again.

Now I can’t get it to Promote at all. I’ve tried removing ALL installed roles (AD Domain, DHCP, and DNS) and rebooting and starting from scratch, but the Promotion just hangs on the first step (where you input the Domain name and credentials).

I’m thinking maybe, somehow, the AD got confused and thinks the Server is already a DC, so it won’t let me add it for a second time?

How can I go about troubleshooting this problem? Alternatively, how can I check what is going on from the AD side when this new server tries to initiate the Promotion process? Is there any way I can possibly purge any corrupted or orphaned references to this new DC in the AD database, before I try to Promote it again?

Further details:
All DCs on the Domain are Windows Server 2012 R2, and the AD is native 2012 R2 as well (it was never upgraded from an older version).
The new DC is being installed at a new site, which connects to the main site via a slow VPN. This may have been the culprit in the initial confusion.