Sq: your lumbar is unlocking just a little, but not because you're going too low. First things first, do you have the bar in the correct position on your back? Impossible to tell from the video, but I'd guess it may be high. You need to shove your knees out and forward as your hips are moving back. A video at a rear 45deg angle will allow for more diagnosis.
DL: Physio-ball shenanigans!
Work on getting fully squoze before you pull.
Refilm from a front 45deg angle.