I don't believe this failure was a result of a defective product. In fact, I'll be ordering a replacement in just a few moments.
On my Tarmac SL3s with DI2 it was the factory hanger that kept stripping threads. I switch to a Wheels one 1100 miles ago and haven't had an issue yet. On the SuperSix Evo, the stock hanger broke after 100 miles and from talking to my MTB friends, they replace the same hangers on their Cannondale Flash frames every weekend.
The hanger that broke on Sunday snapped on the outside of the dropout just below the bolts. I truly believe that this was just a combination of the bike falling over and the DI2 derailleur not having any lateral give what so ever that caused this one to break. I'll drop it in the mail if you'd like to inspect it, but there is no need to send a replacement.
Keep up the good work over there. I've referred my MTB friends to your site so they can stop ordering the cheep OEM ones every week.
Hmmmm....so which is it, a defective hanger (i.e. stripped hanger threads) or broken hanger due to rider wear and tear/abuse (i.e. bike falling over on hanger)?? Either way, it doesn't sound like either of these scenarios are consistent with Di2 specific issues, per claims in your original post.