I’m pretty sure this is a graphical glitch that’s been introduced in the last update (the Paris/France one).
Approx 0.5 miles after the start of Road to Sky, there’s a large boulder on the right which has now moved partially into the road, and I rode through it. At least one of the other people on our private meetup saw this too - we were actually riding the Big Loop course. I know it’s 0.5 miles from the start of Road to Sky because I saw the same thing yesterday when I rode Road to Sky myself.
The attached pic isn’t the best, but shows the rock behind me just after I went through it.