Since I got the message only after doing what I as doing and the message isn't clear, I'm not exactly sure what caused it. However, I got "Congratulations, you've found a bug! This story type doesn't exist!" on my activity feed after updating some stuff about Total War: Three Kingdoms. Since my game information (i.e. PEGI rating) apparently got approved and the only other thing I edited was summary, I can only assume it's a problem with the summary.
Also, on lists of users (such as Owners, Trackers, and Wishlisters), avatars are sometimes zoomed in. You can see it especially clearly on the page for Total War: Three Kingdoms (linked above), but I noticed the problem elsewhere too.
Last edited by Zkuq - on 10 January 2018