1) During the third pull you're shrugging back, way back, practically throwing your upper body backwards. Think of shrugging straight up, focus on that while doing pulls. (OK technically Oly lifters shrug under the bar, not up, but thinking of shrugging up can be a good cue if you're shrugging back).
2) Tighten your back. See how rounded it is when you pick up the bar? You don't want that. Flex your lats and keep the bar close to you, it's the same muscles you want to recruit when doing an RDL.
3) Look forward, don't throw your head up.
4) You may be pulling with the arms a bit but I can't really tell from this angle.
5) Catch it tighter! Part of this is because you're swinging the bar from throwing yourself back though.
Focus on pulling straight up when you practice pulls, and try doing some drop snatches to work on the stability and dropping quick and straight under the bar, and high-hang snatches to focus on that third pull.