Hi guys,
I'm posting my problem here since the thread is not so old.

I have an ultegra 6870 di2 groupset and yesterday the rear derailleur stopped working suddenly while I was riding.

From what I already read on internet looks like it is in crash mode:
- battery is charged
- front derailleur is working
- checked the cables (except for the ones in conjunction unit B which is internally)
- long-pressing the rear shifter will light the battery led and the RD is making a noise for a while but not moving at all

What I tried:
1) pressing the button on conjunction A unit for +5 seconds for recovery mode doesn't seem to work. The red light appears but it is not flashing and keeping the button pressed will turn off the red light and RD is making a short noise. From what I've read, the red light should start flashing and when rotating the cranks RD should go over the entire cassette, but it doesn't.

2) Disconnected the battery and reconnected it after a while

3) Did a successfully firmware update. Now when I long press the conjunction A button the red light is solid and if I keep pressing it, the green light appears too.

Probably the nearest shop with PCE-1 unit is at 8 hours long drive so if you have any suggestion of what else I can try please let me know.
I have read somewhere that it is possible to manually reset the crash mode (if that is really the problem in my case) but didn't find any information about how to do it.

Thank you,
-Paul