I was able to fix the problem for free.
As I suspected the cable was too short and didn't fully engage the right side of the motor. I called a dealer and he told me a fast fix. Since the internal cable shaft can't be made longer the option is to shorten the outside tubing for the internal flex shaft. Approximatly 5/8 inch of the black tubing is secured inside the metalic end fitting that provides attachment points on the end of the tubing. I cut the tubing at the fitting and discarded the 5/8" of tubing that was left inside the fitting.(I heated the fitting with a small torch and removed the melted plastic). Then I heated the fitting and pushed it onto the remaining black tubing cut end. The fitting has 4 small barbs that keep it from coming off. With the outer sleeving 5/8" shorter the inner flex shaft is now fully engaged with the drive motor!!
This appears to be a design problem that can only be fixed by modifying the original factory part.