Sources speaking with Reuters said Apple switched to a single layer of backlight film for the 4.7-inch iPhone 6, but found the screen wasn't bright enough. Display production was put on hold while engineers rushed to redesign components so they could go with a more traditional double-layer setup.
With the redesigned backlight system sorted out, production has resumed and Apple's supply partners are said to be working overtime to try to catch up ahead of the official product launch.
Apple is expected to host a special media event on Tuesday, September 9, to introduce the iPhone 6. Assuming the company follows it's usual post-announcement pattern, pre-sales will start on Friday, September 12, and the new iPhone will be in stores on the following Friday, September 19.
The iPhone 6 is expected to be available in 4.7-inch and 5.5-inch screen sizes, up from the 4-inch screen available on the iPhone 5 and iPhone 5s. The new model is also expected to ship with a redesigned body that more closely matches the iPad Air and iPad mini, offer longer battery life and a faster processor, and sport better cameras, too.
Assuming Apple had to change its display design, that would indicate the company managed to go through extensive pre-production testing without realizing the display wasn't bright enough. While it's possible, it doesn't seem likely that a company known for sweating the little details would miss something so critical to the overall product design and user experience.
What's more likely, assuming there are production issues, is that suppliers haven't been able to get parts to Apple in the quantities they need to produce the number of iPhones the company wants available for next month's launch.
Apple hasn't confirmed when it will start selling the iPhone 6, or even that the device exists at all. It also hasn't confirmed the reported September 9 media event, so for now no one can even say the product launch is being delayed. Regardless of any potential production delays, it's a pretty safe bet that Apple will be strained trying to meet initial demand considering how high consumer interest has been for previous iPhone launches