I had a MAAS install which had multiple name mappings for a given IP address, in turn causing a node's name to be missing from DNS.
maas 1.7.0~beta7+bzr3266-0ubuntu1~trusty1
The node who was missing from DNS was galileo.
As you can see in https://pastebin.canonical.com/119017/ there were two mappings for 10.1.4.2. It was only maxwell that actually had that address, the zone.maas file was old and irrelevant. To fix it I moved the old zone files out of the way (there was another which contained a typo in the zone name) and restarted maas-clusterd, bind9 and apache2. At that point galileo was in DNS and resolving to the correct IP (10.1.5.12).
I remember having to change the FQDN of the node in question since it was .maas and not .local (.beretstack) as desired.
Note I subsequently filled in the correct value for "default domain for new nodes" in the settings.