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What happened to it?
One of the ports died. It was connected to either junction A or the battery, so we lost everything. Swapped the wires around so the FD was on the dead port while waiting for a new one.
Where was it mounted? Was it allowed to rattle or get wet?
Loose in the downtube, so it could rattle and it did fail after a wet race, but I think that may have been a coincidence.
If I were relying on Di2 for crossing continents rather than 10 mile TTs, I'd pack spare junctions and wires.
But you might have to replace junction B - had to do that on father's two year old Di2 bike this year.