Omega Geneve Dynamic winder breaking.

I have a Geneve Dynamic, bought in 1972 basic model no day date. Every 2 years or so the winder comes loose. I have a good friend who is a qualified independent watch repairer, who does the repairs for me, he says this is a weakness in the design. Is this correct? I have just had it cleaned and repaired again, but this time lasted only 2 months before the winder came off the watch. I have always taken for granted that he uses genuine parts. But I have always thought that this is not really the issue here.

Any thoughts would be appreciated, As I now am very reluctant to use it.

Thanks for the replies. I am aware that it's broken when the winder is free-wheeling and not winding the watch up. That is when I realize it can come straight out.

Those 2 part or male/female stems are always a pain and the female part where the crown is attached usually gets weak over time causing it to give way. Better replace both parts and call it a day. And please be absolutely sure it’s a 2 part stem because I’ve seen lazy watchmakers install conventional stems and it was a pain to take apart.

Thanks for the info, I will pass this along. No, he is an independent watchmaker.