In just one sequence during Ethan's cliff climb, you can clearly see chalk climbing marks before he reaches a spot on the mountain. Which indicate that someone has been there before him and he's following the same route. Fair enough...except that no such chalk marks are in evidence anywhere else during the climb. So did the climber before Ethan just touch that one spot? The odds of either Ethan hitting the one spot where the chalk marks are, or the weather having washed off every other chalk mark except that one, are pretty astronomical.