Thank you. The best is for me to see directly with the pro who might send me a new flywheel while I would send him back the damaged part. Once again I would like to understand how all this could happen ?
If you think about it, the flywheel is sitting there, minding its own business, and it's suddenly assaulted by the starter gear, flying out of nowhere, it's bound to get a bit bruised and beaten over the years. Added to that, if it's true that the engine always comes to rest in one of a few positions (i don't know if that's true, but sounds reasonable), then the same few teeth on the gear ring will be subject to the wear and tear. Added to that there is no lubrication, like with most meshed gears. Perhaps your starter wasn't making good contact with the gear ring before you refurbished it, good video by the way, and perhaps that caused more damage to some of the teeth.
I think the gear ring is made to be sacrificial, a bit like the iron rim on a cartwheel, hence why it can be replaced, not bad if its lasted over 50 years!
Just make sure the starter makes good contact with the new gear ring when you assemble it again
So glad it wasn't too much of a problem for you!
