User blog comment:DaNASCAT/Template Types: A Smarter Categorization System/@comment-1038387-20151204212900/@comment-24473195-20151211211948

"Strangely, it went down from 550 to 3 overnight a couple of days back, and then to 0, though many templates were still uncategorized. Then today, it was suddenly back at 400. With the mass tagging action, I got it down to 120, but after a while, it seems the list stops updating upon refresh."

I wouldn't trust the insights list. It is incredibly inacurate when a list has a lot of items, and sometimes even when it doesn't. However, Special:templates is pretty accurate.

There is some serious underlying bug with the insights implementation that they really need to track down and kill.