Keep it up! The platform is awesome, too!
The weight is pulling you forward a bit from the very start. try moving the bar forward 1 inch in your starting position with your weight balanced on your foot (maybe even a touch more towards the toes), and then "rock" backwards onto your heels as the bar passes your knees.
Also, it looks like your hips are the first thing to rise on the lift, keep your back angle fixed until you get the bar past your knees and you start to open up for your second pull.
Hope this helps!