 <p>UIViewControllers may implement didReceiveMemoryWarning that the system calls when your app is on low memory. Framework classes, as core text, are most likely do implement this and act accordingly to save memory. So it is possible that your core text object aims to help your app resolving the low-mem situation with freeing some of its resources that can even cause it to blank its contents. Fix first <em>all</em> memory leaks in your app.</p> <p>On the other hand, all bugs are very difficult to correct if you can't reproduce them. If you suspect that the issue is due to low memory, try to simulate this yourself by allocating huge amount of memory in your application and hope that you can reproduce the erroneous behavior that way.</p>