The arm bend isn't the problem; it's a symptom.
I wouldn't be able to diagnose these from just the ending still frames normally, BUT in this case other frames from the video are visible down at the bottom of the image, and conveniently enough, one of the frames displayed appears to be the one where you are just starting to bring your toes up to the bar, and I suspect that's where your problem lies. In that frame, I see your head coming out and your shoulders closing, and from the angles (and from the fact that this is the most common problem in a kip), I'd guess you're closing your hips and shoulders too early as you initiate the kip.
Try to stretch the glide swing all the way out until you feel it stall in front; the kip should then initiate as you start swinging back down the other way. Hips should bend first, and shoulders should remain mostly extended until your hips pass under the bar, and only then should your shoulders close to push the bar down.
(Another common contributing factor to bent arms in the finishing phase is grip; you actually want a pretty loose grip for a kip, and this will cause you to naturally regrip to the top of the bar)