Since you said in your intro that you try to follow the NPA mechanics model, I’ll use NPA terminology.
Looks like you start with a slight bend in your knees and waist. That’s good. It also looks like you get your momentum started early and lead with your left hip/butt cheek so you’re doing a good job with “lift and thrust” (the 8th imperative that didn’t make it into The Art and Science of Pitching). And you do a good job with swivel and stabilize though I’m thinking there’s a chance you’re swiveling a tiny bit early.
Now for the issues…
First thing I notice is your back foot lifts off the ground instead of dragging. And definitely well before ball release. This can be an indicator of a posture issue - getting the head and shoulders out front too far/soon. It can also be caused by opening up early.
Second thing I notice is that you don’t quite get to “equal and opposite”. You keep your throwing arm bent but you extend your glove arm straight out in front.
I’m going to suggest that your back foot is lifting due to the shoulders opening early, that the shoulders open early because you swivel early, and that you swivel early because your glove arm takes too much time extending out front and then bending so you’re having to play catch-up.
That last part is a bit of a guess but, regardless, I think the first thing you should work on is getting to “equal and opposite” at foot plant. This will give you the timing to delay shoulder rotation. Keep in mind that these are small adjustments.