My apologies it's an error from my part, I didn't noticed the folder mounting in Azure was a Bind and not a Volume mount.
So we was binding an empty folder in Azure File into a non empty folder in the container which wiped it's content. Then we had a startup script that was writing in the root file of the mounting point so I thought there was a probleme with folder creation (but I was wrong, folder were just wiped by the binding and then root file normaly created).
We still have an issue with a service which fail to initilize but I think it's not related to azure.
My apologies for disturbing,
Best regards,
Salim