The first issue I see is that you aren't standing up fully and "finishing" each rep; your knees and hips remain a little bent at the top.
I'm pretty sure you have the bar in a high bar position. It doesn't look like it is resting across the back of your deltoids. I might be wrong, perhaps someone more experienced can comment here too...
I think you could go a little deeper, all of the reps seem a smidge high.
You are trying to keep your back too upright; lean over more and stick your butt out. This could end up coming to you naturally if my hunch about the bar being too high on your back proves correct.
As the set goes on your wrists start curling under to support the bar - bad for business. Keep the shoulder blades squeezed tightly together.
What shoes are you wearing? They look like running shoes.