Pitcher appears to have a sequencing issue in that it looks like he rotates shoulders with or even before hips. One possible cause is he lacks glove side control - he kind of flies open with the glove and then lets it drop instead of stabilizing it in front of his torso. Another possible cause is that he's trying to be quick since he uses a slide step and he looks over to 1B as if there is a runner there.
I would try to establish a better opposite & equal position that better mirrors the throwing arm. Specifically, since his throwing arm seems to wrap around behind him a bit, I'd have him extend the glove towards the RH batter's box instead of the LH box like it looks like he is doing. This should help keep him from flying open with the glove arm, allow him to keep the shoulders closed longer while the hips rotate, and possibly help him stabilize the glove in front of his torso.