I recently changed my main Deco and after that DDNS has stopped working. The IPs I get from my *.tplinkdns.com domain have nothing to do with my IP. I'm not under CGNAT.

I don't know where it is getting the IP that it is reporting to the ddns service from; I can't find that IP nowhere in the Deco app while at the same time it is completely different from my actual IP address.

Disabling and then re-enabling DDNS doesn't fix the issue.

Changing the domain worked, in the sense that the new domain is pointing to my correct IP. However, after today, I now can't revert to my old domain anymore as Deco says it's already in use; That's funny, though, because I've been using that domain since I ever bought this Deco unit. Also, when I run nslookup in my Mac using 1.1.1.1 over my old domain, it returns NXDOMAIN. After that, I decided to look at what dnschecker.org shows for my old domain, and it is pointing to different IP Addresses in different regions of the world (even more than 3h after I've changed the DDNS settings), the same two IP addresses that I would sometimes see it (incorrectly) pointing to:

This looks a lot like Deco/TP Link DDNS service's are subject to some kind of domain takeover attack. As you can see in the image above, the same tplinkdns domain is pointing to two different IP addresses depending on DNS server, none of which are mine and, AFAIK, never were mine (my ISP doesn't work with the 77.* range, for example). And all this was happening WHILE my Deco had the old domain still configured in my DDNS settings (meaning: it was still configured as if I was the owner of that DDNS, even though clearly it was pointing to someone else's IP).