Reuters is reporting that Apple may be having difficulty prepping a sufficient number of screens for the next iPhone. Apple is expected to unveil the new line at media event on September 9. The problem, says Reuters, involves a “key” component that’s disrupting the production of the line’s new screens, rumored to be larger than the iPhone 5’s current four inches, and possibly come in two sizes. More specifically, Reuters’s supply chain sources say the problem is with the backlight configuration in the new phones.