A recent WSJ report suggested the problem the with the AirPods was a getting the independent signals to both earbuds to remain in sync. The well sourced John Gruber of DaringFireball debunked that claim.
It makes more sense to me that Apple has run into a manufacturing problem, not that they discovered a design defect after they were announced. “More difficult to manufacture at scale than expected” is also what I’ve heard through the grapevine, from a little birdie who knows someone on the AirPods engineering team. Things like what happens when you lose one or the battery dies — Apple solved those problems during development.
Gruber also followed up on that report noting that another 'little birdie' has confirmed the same thing, an 'unexpected manufacturing problem at scale'.
Please follow iClarified on Twitter, Facebook, Google+, or RSS to be notified when Apple announces a new release date.