Ok what I’m seeing is in the static leases element of the DHCP and DNS page under the network dropdown. The MAC address elements always have the .lan extensions stored, so irrespective now of whether my device is called phobos, phobos.network or phobos.lan, the MAC address is always being identified as belonging to phobos.lan. This happens whether I have rebooted the devices or the router. It appears that having been given the extension the MAC address is always associated with that name and is not updating that name (even if the name in the static lease is just phobos)
I hope that clarifies things