This is in regards to Campagnolo C-Record downtube friction shifters.
The shifter for the rear derailleur is slipping, especially in the lower gears. For example, when I'm on the largest rear cog (lowest gear) the shifter lets the derailleur slip towards the next cog, ever so slightly, and very slowly. It never slips enough to ghost shift, but just enough to cause excess drivetrain noise. When riding, I occasionaly have to pull back on the shifter to bring the derailleur back into alignment with the gear I'm in. I've tightened the shifter down as much as I possibly could. Is there anything else I can do to help fix this problem? Again, this is DT friction shifting.