dyndns with dual nat

[keropiko]

Hello all,

I recently setup a dhcp wan connection behind NAT. The strange problem is with dynamic dns.
The dyndns gets the internal ip 172.x.x.x and not the real wan ip. It is strange that i have also a 3g wwan connection in the same setup that also gets a private range ip 10.x.x.x but if i choose this interface for the dyndns it correctly picks the public wan ip. The problem is with the wan.

When i run curl -4 url (and any ip site like checkip ecc). It shows the correct wan ip.
Why the opnsense client only for this interface shows the internal ip?
What can be the cause of that?

Thank you