Unbound and dynamic DNS

I have been checking it for several weeks now, I get this kind of errors

info: validation failure <conn-service-eu-05.allawnos.com. A IN>: no DNSSEC rec ords from 176.9.93.198 for DS allawnos.com. while building chain of trust

only if I enter dnsforge.de as DNS server and these servers are not validated by ipfire during the check.
DNSforge supports DNSSEC and DOT, why does this error occur?

The error messages with the DYNDNS service I could eliminate by switching to another provider.