DMZ disables access to modem from xfinity App

I enabled DMZ to an internal system; and once I do that, the xfinity app thinks I'm offline, I can no longer configure other ports.

I was hoping that DMZ would additionally support hairpin port forwarding (like If I have a port fowarded on the public IP I'd like to be able to also hit that port/IP from an internal computer and still have it forwarded internally - often called a hairpin route.)

Your modem configuration team should really consider not necessarily DMZing EVERY thing, which makes the modem inaccessible.