My Fahrrad Manufaktur T100 is finally firing on seven gears again! A welcome development after almost a year of failed attempts to restore gears 1 & 2 to working order.
Andrea, the mechanic at Velorution, ended up replacing the shifter box and the twist shifter itself, now everthing works pretty much as it should (still the odd skip or stick, but no big deal).
The odd thing is that he said he'd onlly seen this type of failure in a SRAM hub in thier heavy-duty work bikes.
The new shifter has quite a different feel to it, but it's growing on me. But the really neat thing is that the direction of twisting is different, which makes it the same as my Rohloff - much less confusing in the long run!