well, i've taken these things apart and put them back together twice now, as per youtube video

http://www.youtube.com/watch?v=K_2G5NgluQM

I can't find anything wrong with them.

(these don't have g-springs, which are responsible for the "clicking" noise, which isn't the problem in this case)

basically the thumb lever has a sweet spot where the ratchet will slip, hence upshifting is rendered useless.

but upon inspection i can't figure out what part is the trouble maker... as the design is pretty subtle...

any help would me much appreciated