New Host not found in DNS

I have found these:

Bear in mind, none of these are exactly the problem I am seeing. I have UCS setup as my main AD (with DNS etc). DHCP is on another dedicated host that is NOT UCS. I also have a backup DC that is running UCS. Everything was working as expected until recently.

Where do look for answers? As I said, there are no errors appearing in bind or syslog.