Two of the weekly data syncs were failing: the discovery run that collects the geofeeds network operators publish about their own address ranges, and the Norwegian national address register. Both showed on the status page as datasets that had never been installed, which was true, and neither had reported a failure anywhere, which is the actual incident.
Nobody was told a wrong answer. What they got was a thinner one: an IP inside a range whose operator publishes its own location was located from the geolocation database like any other, and a Norwegian address was checked against its country's postal format rather than against the register of real addresses.
What caused it
A scheduled command sends its output nowhere unless it is told otherwise, and the two syncs are also run in the background because they download and compile very large files. That hides the output a second time. So a task could fail every week, for as long as it liked, and produce not one line anywhere that anybody would ever read.
What changed
Every scheduled task that runs in the background now appends its output to a log file, and a test walks the schedule and fails, naming the task, if one of them does not. That is the direct fix, and it only helps somebody who goes looking.
The check that does not need anybody to go looking is the daily freshness sweep. Once a day it reads the same list of datasets the status page publishes and warns about anything that is not installed, or whose version has aged past the window that dataset is expected to be refreshed within. It reads the published list rather than a list of its own, so a dataset added later is covered the day it appears on the page. And because it judges the data rather than the job, it still fires when the sync command is not running at all — which was precisely the case here.
What it does not tell you
How long the two syncs had been failing is not recorded, because nothing was recording it. That is the reason the incident is worth publishing: the fault was not that a download broke, it was that a download could break in silence.