Cruise control/overdrive issue in 1996 Altima

In my 1996 Altima (140K mi.) has the following issue:

The transmission shifts and runs perfectly at all speeds, including the overdrive. The cruise control works fine about half the time, but the other half of the time when I hit “set” on the cruise control, the overdrive turns off. The cruise control will set and maintain the right speed, but the rpms are obviously much higher.

I have not found any relationship between this problem and other factors, such as the car’s speed, outside temperature or other factors. The check engine light is not on and there are no codes being stored by the computer.