That exact scenario happened on an escalator that I serviced that had up and down side by side in Cambridge Mass. Stairs ran same direction for over 30 years and someone decided to change direction. A blind guy’s seeing eye dog was so used to going up the same unit and happened to be running down and unfortunately the poor dog's paws got torn up. It’s was a horrible scene to say the least.That's because a dog's toes can get caught and ripped off when the final step enters the comb plate as you're exiting off the escalator.