You need to set your lower back more. It seems you start to set the arch in your upper back, but then it never fully "travels" down to your lumbar. Think of tilting (not raising) your butt up. I also noticed you sometimes relax your back a bit prematurely when setting the bar back down. Your back should be fully set from the moment the bar is off the ground, until it is fully back down. Do not relax it during the left.
Also, keep the bar closer to you all the way up. It seems that you are rushing a little to pop your hips up and removing your legs from the movement a little too soon.
I am not an expert on this, so take my advice with a grain of salt. Maybe one of the more experienced members can chime in.