Sub-server DNS Records

There seems to be an issue when trying to create a sub-server for a current domain in my Virtualmin setup.

I have my server template for sub-servers set to create custom DNS record and the option ticked to add these into the parents zone.

The later works fine, but my custom records are ignored and instead default records for admin, webmail, mail, and MX are created?

I've simplified my custom record template below:

$ttl 38400
 
$ORIGIN ${DOM}.
 
${DOM}. IN SOA NAMESERVER1. ${USER}.${DOM}. (
   ${CURRENT_TIME}
   3H
   1H
   1W
   1D )
 
${DOM}. IN NS NAMESERVER1.
${DOM}. IN NS NAMESERVER1.
${DOM}. IN A ${DNS_IP}
www.${DOM}. IN CNAME ${DOM}.

The custom records work fine on a top-level-server and are created as I expect without the additional records.