Cruise control spontaneously turns itselt off

We have a 2008 Ford Fusion (V-6, 6-speed AT, AWD) that unpredictably turns off its cruise control. I cannot ID a pattern or set of circumstances that cause this. The dealership says there are no fault codes showing, the circuitry tests OK.

Any ideas, suggestions, lines of inquiry? Thanks for your help.

Sometimes a faulty high center stop lamp will cancel the cruise control. (It’s getting a signal the brake has been activated)

Thanks for your suggestion, what is a “high center stop lamp”?

It’s also known as the third brake light. It’s the one on the back of the car in the middle, normally mounted higher than the taillights, hence the name high center stop lamp. The stop lamp switch could also be at fault or out of adjustment, provided this car uses the switch to deactivate the cruise control. Some Fords use a pressure switch on the master cylinder to deactivate the cruise control.

The stop lamp switch

AKA Brake light switch.