Wiki links are not required to exactly match the case of page titles that they cite. Instead we reduce the link to a slug, retrieve the page, and then render the page with the proper title case as recorded in the page json.
A defective Lineup Diagram sees two capitalizations of the same page and thus draws it twice.
This leads to some complexity when drawing maps by tracing links from page to page. We might render a link well before fetching the page only to find out later that the rendering used the wrong case. We might also quit before fetching an actual page and never know what the proper title case might be.
A good fix might be to remember slug ⇒ title when encountered and then back patch any that might have been rendered incorrectly.