Your feet were a little too far behind the girth. That can put you really off balance, and make you lean forward. When you were trotting you were a little far back in the saddle, but that may just be because of your saddle. Your jumping position is amazing in the first slide. I see no flaws. Your elbows are in the right place, your shoulders are back, you are looking ahead, and your heels are down. In the second, you are coming a little too high out of the saddle. At 1:22 your leg is a little behind the girth, and you are a little too high out of the saddle. When your horse pulled forward, it pulled you farther out of the saddle. Try looking down when riding. You should see just the tip of your toes. Your landing are very good! At 1:42, try pulling your shoulders back. Give more with your legs than with your hands. You seem to have a very strong leg, though, and are stretching just right. You have a good hand position, too. You also have a very, very, very, beautiful horse.