Bonjour Roger and Berny,
Thank you for your answers. About O'rings, I will order new ones, no problem.
About the bolt on the part which has rotated (I do not know its name), I have not seen it, this is why I thought about Loctite. I will look accuratly again, and if you can sher with us a picture of this small bolt, that would be great. Do I need to remove the flywheel ?