Apple is facing a significant bottleneck that may hinder the launch of the special edition iPhone 8 this fall, and it’s all down to the TouchID.

Rumors regarding the fate of the iPhone’s fingerprint recognition function have veered wildly from having it built directly into the screen, to moving the button to the back of the device. In reality, Apple might be trying both of these things; the second in response to the difficulties that are being reported in integrating the TouchID underneath the display in the forthcoming iPhone 8.

In fact, it’s being referred to as Apple’s biggest “bottleneck.” A note from analyst Timothy Arcuri based on research and obtained by MacRumors, said the following:

“For the 5.8-inch OLED version, the biggest bottleneck remains integrating an under-glass fingerprint sensor into the display. The current yield rate of Apple’s in-house AuthenTec solution remains low and Apple seems unwilling to use other vendors’ products.”

He then outlined three scenarios that Apple could pursue:

• Apple removes Touch ID from the 5.8-inch iPhone entirely and relies solely on facial/iris recognition.

Though this is unlikely due to a lack of security and the knock-on effect to Apple Pay.

• Apple puts Touch ID on the back of the 5.8-inch iPhone, but in a different place than the one on the Galaxy S8.

Previously reported, but also unlikely as Apple doesn’t consider this user-friendly or optimal.

• Apple delays production of the 5.8-inch iPhone, but still announces the device in early September alongside updated 4.7-inch and 5.5-inch models.

This is the most likely solution, rather than pushing out a device intended to be a big step beyond the releases of the last few years, but Arcuri says Apple continues to work towards a solution that will see the iPhone 8 launch alongside an iPhone 7s and 7s Plus this September.

The MacRumors article goes on to say:

“Arcuri said Apple is aiming to finalize its fingerprint sensor specification by May, but if its in-house AuthenTec-based solution is not feasible due to yield issues, mass production of the tentatively named “iPhone 8″ could be delayed until September, compared to its usual late July to August timeframe.”

Either way, it’s likely supplies of the iPhone 8 will be limited, much like the Jet Black iPhone 7 last year. It might also be completely non-existent following the announcement of the device, instead launching later in the year.