Noisy messages from BIND about root hints change

[Chris Thompson]

One (but only one) of our recursive nameservers, running BIND 9.8.3-P4
we got a whole lot of messages in the log as a result of last week's change
of address for d.root-servers.net:

 Jan  4 06:24:08 recdns1.csx.cam.ac.uk named[9496]: general: warning:
   checkhints: d.root-servers.net/A (128.8.10.90) missing from hints
 Jan  4 06:24:08 recdns1.csx.cam.ac.uk named[9496]: general: warning:
   checkhints: d.root-servers.net/A (199.7.91.13) extra record in hints
 Jan  4 06:24:09 recdns1.csx.cam.ac.uk named[9496]: general: warning:
   checkhints: d.root-servers.net/A (128.8.10.90) missing from hints
 Jan  4 06:24:09 recdns1.csx.cam.ac.uk named[9496]: general: warning:
   checkhints: d.root-servers.net/A (199.7.91.13) extra record in hints

 [... 1972 pairs of messages omitted ...]

 Jan  4 08:50:05 recdns1.csx.cam.ac.uk named[9496]: general: warning:
   checkhints: d.root-servers.net/A (128.8.10.90) missing from hints
 Jan  4 08:50:05 recdns1.csx.cam.ac.uk named[9496]: general: warning:
   checkhints: d.root-servers.net/A (199.7.91.13) extra record in hints
 Jan  4 08:50:08 recdns1.csx.cam.ac.uk named[9496]: general: warning:
   checkhints: d.root-servers.net/A (128.8.10.90) missing from hints
 Jan  4 08:50:08 recdns1.csx.cam.ac.uk named[9496]: general: warning:
   checkhints: d.root-servers.net/A (199.7.91.13) extra record in hints

And then they stopped.

Now I can more or less work out what provoked the first message. We had
already changed our root hints file the previous day (and done an rndc
reconfig) but the old A record for d.root-servers.net was still in the
cache (and was still there much later on 4 January as I explicitly did
an rndc flushname on it for other reasons). One of our regular checking
jobs at 06:24 will have used this recursive nameserver to look up the
NS records for "." and the address records for the *.root-servers.net
names so referenced.

But why did it keep going on and on about it? And what made it stop?
Has anyone else seen anything similar?

-- 
Chris Thompson
Email: cet1 at cam.ac.uk