Bob,
I repaired my self-cancelling function using the shrink tubing trick you mentioned, as described in this Forum. (My turn signals were not self-cancelling in either direction, so Dr. Benz's solution was not an option.) I was skeptical, but that trick really worked! I had my assembly off the car and totally disassembled on the work bench because I had other problems, but you can do it without pulling the unit completely out of the steering column. (BTW, I can confirm that the turn signal assembly is an exquisite viper's nest of springs, pins, cams, levers, rollers and sliders. But no gears, so a cake walk for any experienced watchmaker.)
I did not use CA glue (because I don't know what that is and I don't think any adhesive would stick to the nylon tab), but I did slightly roughen the sides of the nylon tab with a sharp knife to give the shrink tubing something to bite into. And I did use a double layer of shrink tubing. As the tubing shrinks (I used the hot tip of a soldering iron as the heat source), it automatically forms a little nipple at the tip of the tab. If the nipple is too long, the turn signal lever will not hold the turn position (ask me how I know), so just trim a little bit off with a sharp knife. All it takes is one or two thousands of inch of added length to the worn tab. The tab (or now the nipple) works against a cam (not a pin) on the steering column.
I don't remember who came up with this solution, but many thanks to all those who have contributed ideas in this Forum!
Enrique Garcia
Euro '68 280SL 4-speed