The operator of that service seems to be opposed to privacy. Those failures are intentionally caused when it detects certain privacy-respecting configurations, e.g., use of a DNS resolver that doesn't send EDNS Client Subnet information.
PS: When there's a DNS problem, I try different resolvers amongst Cloudflare, Google, and various dnscrypt ones.
[0] http://archiveiya74codqgiixo33q62qlrqtkgmcitqx5u2oeqnmn5bpcb...