I have a very used set of Suntour thumb shifters like this (below) on my mountain bike (converted to dutch-influenced frankencommuter). Only if I torque the bejoozes out of the screw on the top will they even think about staying in gear.
One of them makes no ratcheting sound at all, and the other only sometimes.
Does this mean that the ratcheting mech is worn out and that's just it? Retrofits? Some way to add a washer inside and make them pure friction shifters?