My Rohloff gearhub will only shift between gears 3 and 4 (I think; display long ceased to be readable, but it's two low gears). I tried adjusting the shifter cable tension but it makes no difference. When I disconnect the gearbox from the hub it still doesn't shift.
The owner's manual troubleshooting section has an item "twist shifter does not turn freely", but beyond 3 and 4, my twist shifter does not turn at all, not even under considerable force. When I do shift (heavily) between 3 and 4, I do see a slight movement in the cables. I am not able to manually pull the cables out of the gearbox.
Until yesterday, shifting worked through all gears albeit somewhat heavily. I took the bicycle on a train, where I strapped it. After I got off the train, the problem appeared.
What might cause this?