Need a rear oblique angle from waist height. The bar looks to be too high on your back by the last rep. You're not looking 5'-6' on the floor ahead of you. It looks to me like you're initiating the movement by sitting back instead of breaking at the hips and knees at the same time. Your knees look to me to be coming forward until you're almost all the way down. Needs to be at least an inch deeper.
Read this: Identifying and Correcting Thoracic Spinal Flexion in the Squat | Bill Hannon