At the end of your deliver, control that pivot leg more, keeping it stretched out more that whipping up and recoiling. That recoiling action puts a strain on the hamstring of the pivot leg in addition to “tweaking” the lumbar muscles in the small of the back and spine.
Your pitching cycle looks very strong and well proportioned. You do have a tendency to pick your head up trying to see where your pitch is going - try and restrain yourself from this motion. Finish you complete pitching cycle, regardless if its from the windup or the set motion.
Also, with respect to your whipping action of that pivot leg - if you feel a momentary need to rub your stride knee just above your kneecap, it’s that whipping action of your pivot leg that twists the muscles in your thigh of your stride leg that sends a small twisting action on those thigh muscles. Now that’s nothing serious, just a distraction you don’t need. And it’s not all that noticeable now, but it will be in the near future.