I have only personally had two serious failures of a bicycle transmission system, and both were on a rather new high end Rohloff hub. One was a mechanical failu

I have only personally had two serious failures of a bicycle transmission system, and both were on a rather new high end Rohloff hub. One was a mechanical failure (seal failure causing an oil leak). The other was a complete e-shifting failure caused by the most excellent engineers at Bosch’s failure to allow the shifting system to operate independently of the ebike drive. (The latter is such a severe design error that I think no one should purchase the Bosch+Rohloff system until or unless it gets fixed. Use something else. An ebike is not a car, and it should be operable as a rider-powered bicycle even in the event of an electrical fault.)