title: UIPageViewController navigates to wrong page with Scroll transition style
body: <p>My UIPageViewController was working fine in iOS 5. But when iOS 6 came along, I wanted to use the new scroll transition style (UIPageViewControllerTransitionStyleScroll) instead of the page curl style. This caused my UIPageViewController to break.</p>
  
  <p>It works fine except right after I've called <code>setViewControllers:direction:animated:completion:</code>. After that, the next time the user scrolls manually by one page, we get the wrong page. What's wrong here?</p>