Your back extension looks much better, but you are losing back angle for the first half of the movement. This loss of back angle will turn into rounding when you push the weights back up.
I think the fix for this is pretty simple: keep everything like you had it in the video, but start your setup with your shins about 0.5-1" closer to the bar when you're standing straight up. This will start you at a more horizontal back angle and give you room to get the bar around your knees.