Apple Inc. (NASDAQ:AAPL) has scheduled a major media event to unveil its highly anticipated iPhone 6 on September 9. But the release date could be pushed back. Even if Apple manages to launch the device has previously planned, it may limit the number of smartphones initially available to consumers. Supply chain sources told Reuters that Apple suppliers are struggling to get enough display panels for the iPhone 6 after the company decided to redesign a key component, which disrupted screen production ahead of the launch.

iPhone 6

Apple wanted to use single-layer backlight film in the iPhone 6

It’s the latest evidence of the challenges and risks suppliers face to comply with Apple’s tough specifications. In the past few months, the iPhone 6 has faced battery problems, a separate screen technology problem and other issues as the Cupertino-based company tried to make thinner screens for the device. Most of those problems have been resolved.

Sources said the screen production suffered a setback when Apple decided to redesign the backlight that illuminates the display. The existing iPhones have two layers of backlight film. But Apple wanted to cut it back to a single layer to make the thinnest phone possible. The company’s move put the display panel assembly on hold for a large part of June and July.

iPhone 6 launch likely to drive Apple stock even higher

Unfortunately, the new configuration Apple engineers came up with was not bright enough. So, the backlight went back to the drawing board to accommodate the second layer. Production is now back on track, but suppliers are scrambling to make up for the lost time. The iPhone 6 screens are produced by Sharp Corporation (ADR) (OTCMKTS:SHCAY) (TYO:6753), LG Display Co Ltd. (ADR) (NYSE:LPL) and Japan Display Inc (TYO:6740).

The iPhone 6 launch is expected to drive Apple stock, which rose to an all-time high earlier this week, even higher. The tech giant forecasts strong demand for both versions of its iPhone 6. It has asked suppliers to assemble at least 80 million units of the new phone by the end of this year.

Apple shares fell 0.23% to $100.35 in pre-market trading Friday.