There's another error I noticed (alongside infinitely-loading search results) that looks to be related. Drop-down lists also infinitely load, despite clearing cache, disabling ad blockers, and using a different browser. Refreshing the page freezes selections in place.

It seems that @Elmidae just experienced this as well: https://en.wikipedia.org/w/index.php?title=Wikipedia:Articles_for_deletion/Alien_Cabal&oldid=933049194 came three minutes after the attempted tagging, see contribs and edit summary.