[koates]

You have not stated what vehicle and what distributor but I guess it is the divers helmet type. I have repaired several over the years that have the drive tang damaged by trying to fit them incorrectly. One even had a broken housing because it would mount up squarely to the timing gear cover. As an engineer you should be able to have a close inspection of the shaft, housing etc to see what is going on with it. Post some close up photos of it. Regards, Kevin.