As you squeeze up, you're letting your hips drop just a bit, and the bar moves forward of the midfoot just a bit. As a result, a) you don't get squeezed up enough, and b) the bar is drifting forward as you start the pull.
So, shins a little more vertical, lock those hips in place, and squeeze your chest up as hard as you can.
You're also dipping/bending the knees a little as you initiate the pull. So, you've lost any tension that you generated while squeezing up.
Instead, create tension in your body by driving your feet into the ground (just enough to create tension, not enough to start the pull) and squeezing the chest up to take the slack out of the bar. Once you're nice and tight, then drive your feet harder to initiate the pull.