I agree with
@Bauer, hinge could be deeper and need to hold the plank before hinging on the downswing. But two things to focus on even before that:
1) Your setup. It looks great, except that your shoulder is not packed. Grab the handle of the bell and draw the shoulder down towards your hip by tightening the lats under your armpit. Then,
keep it there throughout the swing.
2) The standing plank - it isn't much of a plank, it looks like you're focusing on getting the bell up. Forget the bell. Focus on bringing your body into a tight vertical board (plank). Then hold it as long as possible until your arm begins to reconnect to the ribcage. Then hinge for the backswing. The bell will do what it should if your body does what it should. As your body comes into that tight plank on the upswing, the power then comes from ALL the muscles. Right now it looks like you're using your hips only to drive... which
sounds correct, but hips driving is actually quads, glutes, hamstrings, abs... all coming from hinge to plank together in a powerful movement, like when you jump. Imagine if you tried to jump forward with just a hip movement! Not nearly as effective as using all the powerful muscles together.
As for the arms, it does appear that you're holding some tension there. The hips drive, the arms guide. The arms are just a rope... try to have them more relaxed.
And although these sound like big things (and they are -- you'll be amazed at the difference when you make the changes!), your swing is not all that far off from where it needs to be. Keep at it, and let us know how it goes!