Does that switch kill the throttle? And, if it's sticky, would it cause a lag in throttle response after lifting off the brakes and hitting the gas?
How many switches are there on the brake pedal arm?
With Nissan, there is a brake light switch and a switch specifically for the CC.
The CC switch needs to be in the closed position in order for the CC to even turn on.
The CC switch and the brake light switch are switched opposite.
One is normally open and one is normally closed.
The CC is normally closed until the brake pedal is applied while the brake light switch is normally open until the brake pedal is applied.
The BCM reads both and needs the correct signal from each one for proper CC operation.
I have not looked into how GM does their CC, but that is something to consider with your brake pedal switches.