I was awarded a tag badge, and the new profile page congratulated me (in this top-left reputation box on my Activity profile, where the "Next tag badge" gets tracked).
Instead of linking to
it linked to
which is a 404 page.
All other links to this badge on my profile (e.g., in the "Badges" section, the "Badges" tab, the "Badges" box on the Activity profile) seem to be correct.