I have a 1981 240 D and the sunroof works great when it it hot but not when it is cold. It acts like it is sticky but the tracks are clean and the cable (male-female) inside the sunroof is clean also. Can the motor get weak over time and it is easier to operate when heats up and the parts are looser and slide easier? This is my first question on this site and am excited that I could get advice !!!