From OTRS: https://ticket.wikimedia.org/otrs/index.pl?Action=AgentTicketZoom;TicketID=11675710
Bug seems related to articles whose title ends in ?, and another article exists with the
same name but no ?.
Examples: see articles [[Josie Davis]] and [[Mayim Bialik]]. These articles contain links
to an article concerning a film, [[Kalamazoo?]].
When I browse Wikipedia using the Chrome browser on Windows 10 and click on one of those
links, it takes me to the intended article.
But if I use the iOS Wikipedia app and click on the link, it takes me (via a redirect) to
the article concerning the city in Michigan.