_acme-challenge cname (as per acme-dns) broken

I contacted my provider and they confirmed that the issue is with their nameserver not delegating the acme-dns zone correctly, and promised to fix it.
While debugging this problem I found two tools I will keep handy in the future for checking delegation issues like this:


I think that if each zone (specifically the one containing _acme-challenge entry) were to explicitly define the name servers used, one could walk from "." to your txt entry (without fail).
[and should be an easy test to conduct]