The main URL is redirecting to “s/exhibits”, so the site with the slug “exhibits,” and that’s itself directing you to “sitelogin/exhibits.”
The first redirect to “s/exhibits” looks just like the normal kind of thing that happens when you pick a default site. The second… that looks more like a module. Judging by the “sitelogin” in the URL, I’d hazard a guess that this might be related to the RestrictedSites module?