In particular, according to MacRumors, "persistent software problems" are causing delays with implementing wireless charging and a 3D sensor in the new iPhone. In addition, other reports have suggested that Apple has still not finalized the placement of the phone's Touch ID fingerprint sensor.
The wireless charging feature - said to be based on an inductive charging technology - may, reports say, be implemented using an external accessory charger that may not be available when the iPhone 8 begins shipping. According to Fast Company, the phone will use a version of the Qi wireless charging standard with components supplied by Broadcom. However, say the reports, the feature may not be enabled until the next iOS update - version 11.1.
Also rumored is the inclusion of a 3D sensor in the phone's front-facing camera, to be used, reports speculate, for facial recognition scanning. Apparently Apple is also experiencing some software issues in getting this feature to work reliably, fostering speculation that this feature too might not be initially enabled at the iPhone 8's launch.
Along with this rumor was speculation that Apple might be planning on using the 3D sensor to replace its Touch ID fingerprint sensor authentication approach with a facial recognition system. However this is not being taken too seriously by experienced Apple observers who note the Touch ID's already proven technology.