yeah, i think something is funky with that hostname. ipdns[12].channelsdvr.net are answering with an A record appropriately -- but then they also delegate the answer to ns[1234].dnsimple.com. i think it should be either/or, but not both.
dvr1$ host resolver-check.u.channelsdvr.net
resolver-check.u.channelsdvr.net has address 172.68.68.82
Host resolver-check.u.channelsdvr.net not found: 3(NXDOMAIN)
Host resolver-check.u.channelsdvr.net not found: 3(NXDOMAIN)
detail:
gtld servers delegate channelsdvr.net to dara & kevin.ns.cloudflare.com
dvr1$ dig +norecurse +noall +auth +answer @a.gtld-servers.net channelsdvr.net ns
channelsdvr.net. 172800 IN NS dara.ns.cloudflare.com.
channelsdvr.net. 172800 IN NS kevin.ns.cloudflare.com.
dara + kevin delegate u.channelsdvr.net to ipdns[12]
dvr1$ dig +norecurse +noall +auth +answer @dara.ns.cloudflare.com u.channelsdvr.net ns
u.channelsdvr.net. 300 IN NS ipdns1.channelsdvr.net.
u.channelsdvr.net. 300 IN NS ipdns2.channelsdvr.net.
ipdns[12] delegate u.channelsdvr.net to ns[1234].dnssimple.com
dvr1$ dig +norecurse +noall +auth +answer @ipdns1.channelsdvr.net u.channelsdvr.net ns
u.channelsdvr.net. 3600 IN NS ns1.dnsimple.com.
u.channelsdvr.net. 3600 IN NS ns2.dnsimple.com.
u.channelsdvr.net. 3600 IN NS ns3.dnsimple.com.
u.channelsdvr.net. 3600 IN NS ns4.dnsimple.com.
ns[1234].dnsimple.com do not have answers for resolver-check.u.channelsdvr.net (nxdomain):
dvr1$ dig +norecurse @ns4.dnsimple.com resolver-check.u.channelsdvr.net a
; <<>> DiG 9.11.5-P4-5.1+deb10u7-Debian <<>> +norecurse +noquestion @ns4.dnsimple.com resolver-check.u.channelsdvr.net resolver-check.u.channelsdvr.net a
; (2 servers found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 21336
however, ipdns[12] do have answer for that host:
dvr1$ dig +norecurse +noall +auth +answer @ipdns1.channelsdvr.net resolver-check.u.channelsdvr.net a
resolver-check.u.channelsdvr.net. 604800 IN A 100.11.85.230