Does the drives you are using look like the one in post 12 or does it have a machined edge where it goes into the hex?
If it’s the latter that’s why it’s failing. Although I can’t think of a drive I’ve seen that was pinned and not machined with a radius going to the hex.
I was talking with a friend of mine who is older than me a bit and he said when guys were running straight 50 and 60 grade oils were spinning the gear on the shaft on cold starts when the weather dropped below 50 degrees.
Evidently that’s where the pinning came from. No one should be running oil like that today.