Hello!
As a result of a user report https://www.mediawiki.org/wiki/Help:CirrusSearch/CompletionSuggester#Does_not_find_internamespace_redirects, I've filed T129545 https://phabricator.wikimedia.org/T129545 and set the priority to "Unbreak now!". I've chatted with Erik about this briefly, and he said he'd investigate. I'm writing this to the list because I think it's good practice when super high priority stuff is dropped in the sprint. :-)
Thanks, Dan