I wonder what is wrong with your Garmin? It sounds like you two had an awesome ride. Good to know that they have done some repaving on Crystal, but I still don't think it's worth doing.
You could have been experiencing "cardiac drift." During the course of a ride, your HR can go up for a given RPE due to dehydration. Your blood thickens, which forces your heart to work harder.
This ride should give you a lot of confidence for Whistler.