title: Assertion failure in UIQueuingScrollView didScrollWithAnimation:force:
body: <p>I've got a <code>UIPageViewController</code> set up paging my <code>ImageViewController</code>.</p>
  
  <p>The <code>ImageViewController</code> contains a <code>UIScrollView</code> with a <code>UIImageView</code> inside.  Nothing else.</p>
  
  <p>I'm testing at the moment with 3 "items" in my datasource for the <code>UIPageViewController</code> (i.e. three pages).</p>
  
  <p>It all works fine and I can scroll and zoom and then page for about 30 seconds and then suddenly I get this warning...</p>
  
  <pre><code>*** Assertion failure in -[_UIQueuingScrollView _didScrollWithAnimation:force:], /SourceCache/UIKit/UIKit-2372/_UIQueuingScrollView.m:778
  </code></pre>
  
  <p>I've got no idea where to start debugging it though as it doesn't point to any of my code and there isn't any of my code in the stack or anything.</p>
  
  <p>Can someone give me a pointer as to where to start debugging this.</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>I've done a bit more testing.  It seems to happen if the scrollView is decelerating (i.e. after a flick) and then I try to transition the PageViewController to another ViewController as the scrollview is still moving.</p>
  
  <p>The app crashes about 20% of the way through the transition to the next page.</p>
  
  <p><strong>EDIT 2</strong></p>
  
  <p>The error seems to stop on the line _cache_getImp (not sure if that's a capital i or lowercase L).</p>
  
  <p><strong>EDIT 3</strong></p>
  
  <p>This gets better.  I just downloaded Apple's PhotoScroller sample app to see if they got round the problem a different way.  Well, no, they didn't.  The sample app crashes in exactly the same way mine does!  You have to zoom and scroll and transition pages at the same time to make it more likely to crash but it happens on it's own too it just might take longer to happen.</p>