Hi,
Not sure that you will thank me for this but when I had a similar problem with the drivers door on my Aeromax, it turned out to be worn hinge pins. At least that is what I was told by my factory service contact told me was the problem, certainly when they were changed the annoying metallic snapping noise disappeared. However it is apparently not a 5 minute job to change them, requiring the front wing to come off to get at the hinges. I think you probably want to get someone who has plenty of experience of working on these cars to do the work. If you are located anywhere reasonably close to Malvern, I can recommend someone to you. PM me if you are interested.
Hope you manage to get it sorted as you are quite right the noise is very annoying.
Regards
Malcolm
