Next time, please get a video from the rear 45 degree angle, it's easier to work with. From here, without doubt, you need to fix your head. You lift it and you lift it even more as the set progresses. You can see what that's doing to your ascent and your upper back. You need to work on controlling your knees more, too. They shouldn't go so far forward nor should they shoot back so soon (your stance may also be off).