I had a custom filter for questions in tag co.combinatorics with no answer. It seems to be "stuck" in the sense that if I go to the "generic" page for that tag, https://mathoverflow.net/questions/tagged/co.combinatorics, the window title is "Custom filtered 'co.combinatorics' questions" and only questions with no (upvoted) answer are shown.
Moreover, if I go to any other tag page (e.g. https://mathoverflow.net/questions/tagged/integer-sequences) the window title says "Custom filtered ..." and only questions with no (upvoted) answer are shown.
I say "had" rather than "have" in the first sentence because I tried deleting the custom filter, and that doesn't fix the problem. It seems that the only way I can view an unfiltered tag list is to open a separate browser or an incognito window and load the page without logging in.