IOS 7: UINavigationBar not in UINavigationController does not make transparency transparent

Question

I have a UINavigationBar (not in the UINavigationController) in my view hierarchy, but sometimes it doesn’t paint its translucent background correctly. In the image below, I have a navigation bar with barTintColor = [UIColor redColor] and the content below it. For some reason, the left and right sides are transparent. Why is this and how can I fix it? (I also think I have more of this after upgrading to iOS 7.1.)