I have used my 5D2 with the remote control many times and I have not observed anything wrong.
When I have time I will try the cap experiment.
I would have said it was all gravy as well had it not been for shooting in portrait..
It took me 18 months to notice it on this particular body.
Rarely do i shoot in bright sunlight unless its as a sunrise/set which wont have the light to my left and above.
I will be contacting Canon for an explanation
1 body fair enough it could be a problem since i got it (doubtful but they would try to get out of it) but 2 bodies same place thats a design fault that although the camera is out of warranty should still require a response and if pushed a resolution for it due it its nature the camera bodies left the factory with this problem and i reckon if the mkiii has the same arrangement its also likely to suffer from this as will any camera body in the range potentially..