A problem with a key component for the screens of the handset has interrupted the production, Reuters reports.
This could cause a delay in the release date of the smartphone or limit the number of units available at launch.
The publication writes that the specifications imposed by Apple to its suppliers usually give them a lot of challenges.
Cupertino reportedly had to start with the production of its smartphone from scratch after noticing a small defect in the display backlight.
A source told Reuters that Apple had decided to include a single layer of backlight film on the screen of the iPhone, presumably to decrease its thickness.
Japan Display, Sharp and LG Display are listed as the suppliers responsible for manufacturing the display of these devices.
Apple is rumored to have scheduled a presentation on September 9th and is expected to release the new iPhone on that date.