I had some issues shifting with my left shifter, I couldn't shift to the smallest chainring anymore and I had the feeling I was missing a click. I thought I usually heard two clicks when upshifting and now there's only one. I opened up the shifter (nice to see the mechanism, it's actually not that complicated) and I notice that the white part that holds the cable doesn't return to the original position when I shift. This I guess explains why I can't censored to the smallest chainring anymore, any idea what's causing this? And can I repair it?