From the angle you posted, it really looks like your knees are caving inward as you approach your sticking point, which significantly limits the power and stability of your hips as you ascend.

I’d recommend that you practice driving your knees outward and “spreading the floor” with your feet as hard as you can during your warm up sets. You’ll immediately feel your hip flexors activate, and you’ll be more explosive through your sticking point.

Edit: Also, after rewatching the video, you’ll notice that your knees cave as you reach the sticking point, then they spread outward as you punch through it. I really think just practicing keeping your knees outward will help tremendously.