Over exposure of images

unfortunatly, all I can offer you is an accurate testing for the settings, in order To verify that the camera cannot make a proper exposure. Go outdoors on a sunny day, put the camera on manual, aperture to f8 and shutter speed to 1/500 and ISO at 100. You should get a pretty good picture with proper exposure.
This is the "Sunny 16 rule", F16 at 1/125 ISO 100 which is EV15. Correct exposure for a clear sunny day, not in the shade.

if it fails, I would say there's some problem in the mechanizm, probobly one that requires a technician, or at least more knowladge than I can offer you.
good luck.