A detector I built was scoring 0.067 recall on temporal errors, meaning it caught about one in fifteen of the wrong dates it was supposed to find. Wrong dates are supposed to be the easy category: extract the years from the claim, extract the years from the source, compare. There is no semantics to get wrong. I assumed the extraction was broken and went looking for the bug.The extraction was fine. The benchmark was the problem, and not in a way that showed up anywhere in the code. The contexts had been written in the wrong voice.