I unsuccessfully fettled the gears on the Kaffenback. In the last couple of days, I've managed to jam the chain at both ends of the cassette, which takes some doing! I think the changer has got progressively over gunged with dirty, which is stopping it cleanly moving.
At the moment I've adjusted the lower endstop so that it doesn't go into the smaller sprocket at all.
I've checked the cassette is mounted OK (it is), and I've looked at the cable to make sure it's not frayed and catching in the outer or levers (it's not). I really need to take the changer off and clean it, but I don't have time before the last FNRttC tomorrow night, so I'm going to liberally spray it with some light oil when I get home this evening, and hope that clears things up a bit. Worst case scenario, I just get it to stay in one gear, and use it as a singlespeed. Last year I cycled every FNRttC on a singlespeed, and it wasn't too difficult, other than Ditchling.
I don't know, you put a bike together, do a measly 6000 miles on it, and things start failing. Wowbagger's right, derailleurs are a bad idea.