I pulled the brake switch last night. I tested both sets of contacts numerous times on the bench and then reinstalled the switch in the bracket and tested the switch using the brake pedal. So far I can't get either contact set to screw up. But, it is cheap so I'll get another.

I think I'll put a new battery in as a precaution - it is 6 1/2 years old and the BAS/ESP malfunction occurred (this time - the first occurrence the car was on the road) during that start cycle when I am seeing as little as 8 volts.