OK, what I m going to tell you ,you may think is crazy.. but its not..many of us have had that malfunction ....on the early C5s, there is a wire chafing problem in the harness that goes to the right door control module ...open the door, there is a black acordian looking wire conduit conecting door to hinge pillar.. disconect one end and shove the harness wiring in,out, twist, etc....hard! this usually solves the problem, if not , your gonna need to gfet in that harness and find the chafe...good luck, this has fixed at least a dozen cars I know of