Sadly, even after cleaning all parts with alcohol they still don't work.
It seems that there is lateral play in the shifters. By that I mean even after tightening the bolt as tight as safe, the individual shifter can move slightly, side to side. It seems that while the rubber washer is on fully, there is a thin sliver between the rubber and the silver plate (part 611/2) where it doesn't fit tight to the silver plate.
I wonder if these are band-on shifters that have been "repurposed" as brazeon shifters.
Does that matter?