Google DNS64 misconfigured?

Wed Sep 27 05:00:56 UTC 2017

I had an ipv6-only lab environment cease being able to browse much of 
the internet on Monday.  Tracked the issue down to google's public DNS64 
service; the following queries should return DNS64 responses from the 
64:9bff::/96 prefix, however, I'm getting 0 DNS64 answers from dig on 
both their servers for the last 60 hours:

dig @2001:4860:4860::64 ipv4only.arpa AAAA
dig @2001:4860:4860::6464 ipv4only.arpa AAAA

DNS works fine, just not DNS64.  A forum topic [0] suggests this 
behavior might be intermittent but no official response from google 
there.  Is google's public DNS64 down for anyone else?

[0] 
https://groups.google.com/d/topic/public-dns-discuss/dD_lSPfqXHA/discussion
-- 
Joel Whitehouse