I had exactly the same issue on my new Roadster when I acquired in 2013. It developed a "scritching scratching" sound which sounded like it was coming from the door or the sidescreen mounts. After putting Vaseline on the mountings the problem persisted. It transpired that it was the leaf springs and the leaf spring bushes - they were in need of some lubrication and this cured the problem. Because of the location of the leaf springs it sounded as if the noise was coming from the doors. If the problem continues I would get your dealer to check the leaf springs. Or if you are more adventurous you can lube them yourself with chain oil.
See my thread here for further details -
http://www.talkmorgan.com/ubbthreads.php/topics/135557/squeaky-side-screens#Post135557
