On that first rep on the 430 x 2 and both reps on the 420 x 2 (only because you stood up to reset, nothing wrong with doing that) your tight at the start but not taking the slack out. You should feel weight in your hands before you pull the bar. This will help you create more tension through out the body at the bar breaks the floor.
This is why the second 430, while being slower, looks a little less jerky than the previous.
