I'm glad to see John's post because as a pilot we do train for unanticipated events such as failures of controls or devices that require quick and correct intervention.

When my cruise did not disengage with brake application many moons ago, I had no immediate pressure to get the coach stopped, so the brain fart we all experience when faced with an unexpected problem that requires attention NOW did not occur. I was able to play to see if the brakes would disengage the cruise (they would not), and then I tried the white button (it would not), so I just turned off the switch which did disengage the cruise.

The next time I used the cruise it worked fine, but from that experience I developed the habit of never expecting the brake to disengage the cruise. My practice now is to disengage it with the white button ahead of when I anticipate slowing or stopping and I never use it when I can anticipate I will have to slow down frequently. That might explain in part my 62.5 MPH speeds.

I have found some side benefits to operating the cruise as I do. John mentions being able to identify switches by touch. Since I am always using the white button or the rocker switches to control the cruise I no longer have to even look down. My hand goes to the exact button I intend to operate and there is no conscious thought involved. That's a good thing because I can react correctly without thinking and being delayed by the brain fart. (Trust me, at the first signs of an abnormal situation that requires your immediate attention your brain goes blank while it tries to process what is happening. That is why John's mention of training is so critical.)

Perhaps today we can identify and verify the cause. That is a secondary consideration because when you need to stop and the cruise does not disengage you will not be thinking about changing relays. You will be looking at the car ahead or the stop sign getting very close very fast.