(note: I purchased my car with the engine out. Now it is about ready to put in, but I'm going through anything I can think of to fix before I drop in the engine.)
I just finished with a "round" on the turn signal. Mine would not stay up or down, and I did not know if it canceled, the steering wheel was not centered.
Since I had to replace the bushings on the coupling down at the steering box, I thought I'd do all this at once. I removed the steering box and coupling, then played with the steering wheel. It was a mess. With the wheel spokes horizontal, the cam for the turn signal was not correct. After taking the wheel off, I lined the cam, but the turn signal would not latch. Some silicon spray got it to work about half the time.
With it out, I noticed the little pins that fit into the detents were not vertical. So I thought I'd bend them straight - wrong, I broke one off!
So with nothing to lose, I took the whole thing apart. (not recommended) The little arms with the pins for the detents, each swivel on a pressed in rivet that acts like a hinge. The top of the rivet is peened to keep the lever on. I had pulled one little lever over the top of the rivet. I carefully put the lever back on the rivet and peened it over again, not as nicely as the factory, but it held. To get to this level, I had to remove the turn lever from its pivots, and that was really difficult to return. Twice. I put it on upside down the first attempt. This is all done sitting in the driver's seat with the turn signal in my hands, the plug will not fit through the steering column without removing the column.
After about 3 frustrating hours, I got it all back together and it works! It latches, and cancels like it should. Since the car is not running, I don't know if the electrical functions work yet.
As to buying a new turn signal, SLS has them on their web site for 345Euros, so about $400+? To get it installed is a mess since the plug will not fit through the steering column with the column installed. If it were something I'd try to do, I'd take the plug apart and pass the wire with just the little male pins through the column.
Good luck, and let me know if you wish to sell your core, the old one. My rivet is living on borrowed time!
Ron