Manually clear dns cache on mavericks

My DNS cache is broken for a few websites (most notably codeship.com) so I need to clear it.

As instructed on numerous websites I've run

dscacheutil -flushcache; sudo killall -HUP mDNSResponder

in various permutations, including rebooting, but it has no effect.

When running dig I get no ANSWER SECTION, but I don't know how to interpret the rest of the info.

; <<>> DiG 9.8.3-P1 <<>> codeship.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 15470
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;codeship.com.          IN  A

;; Query time: 54 msec
;; SERVER: 192.168.1.1#53(192.168.1.1)
;; WHEN: Mon Dec  1 23:37:49 2014
;; MSG SIZE  rcvd: 30