I have ETAP on two bikes, one is symptomatic, the other is not.

The symptom is that the rear derailleur stops responding / shifting (mid-ride) as if the battery were dead. I initially thought the problem was that it was draining the rear battery while parked... but "wait and watch" has indicated that the batteries are not dead, just that electronics go flaky, oddly, starting out fine, but flaking out while actually out riding.

The resolutions to date have been freakishly random.

One time, I shifted the front down then back up, just to see if the front still worked... and then the back started working again. WTF? Usually however shifting the front does not reset it.

One time I swapped front and rear batteries and both started working again.

One time I removed the back battery and simply put it right back on and it started working again.

One time I swapped front and rear batteries and the rear started working and the front stopped. Oops. My bad. That was just a dead battery lol.

One time I swapped front and rear batteries, and the front continued working and the rear did not. As I was heading into some serious hills, I turned around to head back. I dunno why, but I stopped and swapped the batteries again, just for perverse kicks... and it magically started working again! So I turned back around again and finished my ride.

It has never happened (so far at least) twice on the same ride.

It seems very much like a software crash to me. Anyone ever hear of anything like this?

I did end up getting it from a LBS so I have full US warranty. I'll drop it at the shop and make it their problem eventually.

But I'm really hoping there is either a software fix or a warranty replacement that I can do myself (as shop trips eat up mega free time for me).