Since I stumbled over that issue on my instance and could not find anything: the check type dns via Nagios check_dns plugin failed after the latest update.
The reason is a change I was not really able to find anything about, though it was discussed previously on github.
The service configuration changed into a way more logical usage 
. Now the field Remote Host specifies your server that should execute the DNS query for the check, the field Parameters is utilized to specify the name of the record for the query.
Before a valid specification was necessary via parameters: -H [name] -s [host].