This cat is automatically added to images with broken file links but it's not properly removed if the problem was on the image description page and the situation had been fixed (missing image uploaded) - Images stay in this cat although it's not visible on the image page anymore. They are only removed on the next edit or via null-edit.
Neither purging the cat nor the image page removes the cat, gadgets like cat-a-lot can't remove it either because the cat is not present for them.
Reported for Commons with currently 2.500 images in this cat, many/most of them seem to be false positives.
Even after modifying MediaWiki:Broken-file-category to have User pages in a separate cat not a single of the ~3.000 pages has been placed there, requires a null-edit to have an effect on the cat placement (or removal).
Without editing the new cat is shown on User pages originally placed in the old cat although upon editing they are shown as member of the old cat.