Are you *absoultely* certain that the config was not fiddled with at the time of this event?
After grepping some logs, seems 13/12 was the day of a Tor upgrade :
2015-12-13 10:47:31 upgrade tor:amd64 0.2.7.5-1~d80.jessie+1 0.2.7.6-1~d80.jessie+1 2015-12-13 10:48:39 configure tor:amd64 0.2.7.6-1~d80.jessie+1
Timing is good compare to the 10:48:46 of the consensus !
But I don’t remember a config change after that, perhaps only on /usr/share/ tor/tor-service-defaults-torrc or on a default config param change ?
And perhaps the Tor reboot cause the DirPort to be temporarily disabled (seems not human, only 2s duration) ?
Regards,