Using RDGW with AD computer groups and different DNS records

I'm trying to move all of my RDGW RAPs to use Active Directory computer groups. In testing, I've found that when outside of the network, I am unable to connect using a DNS A record that points to the hosts IP address but am able to connect when using the default DNS record that contains the hostname. When inside of the network, I can connect using either DNS name. This is 2012 R2.