2003 Trailblazer EXT with 4.2l engine. I'm a skier so regularly drive from the lowlands to the local ski area which is at 4000ft altitude. The cruise control works flawlessly on the way up the mountain but after being parked at the resort for a few hours then hitting the road to drive home, the cruise control doesn't work. The next day it will function properly. If I make a stop at a store on my way home from the ski area, the cruise control will work just fine again. This has been consistent for several trips to the ski resort. Any ideas on what I should look for as the problem. There are no other failure indications.