Sorry to say this, but have you tried remotely typing in your public IP instead of DNS? Just to try it out. My guess is that typing the IP instead of the DNS should work, as I understand. Right?
In my example:
type 192.168.111.15 instead of name.domain.com
and tell me if it works.
If you have any reverse proxies try to set some exceptions in your network if possible.
I just need this evidence to understand.