regarding distorted back button on iOS app using UINavigationController

I am using UINavigationController in my app. In most of the iPhones I tested its fine. However, on an iPhone4 the back button is sometimes (not always) distorted.

Can anyone kindly tell me if theres something I have missed or if there is something I s开发者_StackOverflow中文版hould do?

Thanks.

This may be a long shot, but check your logs to see if you're get any errors related to core animation and/or bad transforms. I've seen something like this before.