I have a less than year old 5 D Mark III. The main dial becomes unresponsive several times. When this happens, I cannot change any of the camera settings using the main dial. The dial turns but nothing... also a little portrait symbol shows at the top/middle. This happens in both manual and aperture mode. I have to reset the camera settings using menu to get it to respond... I emailed canon... their response, removing/changing internal battery does not work. It has nothing to do with buffer because it normally happens after a break from shooting.. can anyone help?