The page still loads in HTTPS, but turning off HTTPS-only mode means that the HTTP requests succeed, at least more than before. So I guess there's nothing wrong

The page still loads in HTTPS, but turning off HTTPS-only mode means that the HTTP requests succeed, at least more than before. So I guess there's nothing wrong there. The blue ticks actually don't work, though. They're always accompanied by red and seem to be timing out instead of the usual exceptions.