My swing usually gets better as the round goes on, or swings up and down without a clear trajectory. Sounds like maybe a mental game issue. Maybe you let some bad thoughts creep in too much, too obsessive over the mechanics, and stand over the ball thinking, "Don't hook it" instead of some positive swing thought?
Also, with major swing changes going on, maybe you're warming up well and then the old swing starts creeping in more as the round goes on, jumping in even more as your mental game deteriorates after a major screw up or two?
Last thought. Doing 10 dry swings before each shot (I hope you're not doing all of those when it's your turn to hit, or in view of someone who's hitting!), obsessing about the whole array of mechanical adjustments and associated feels you're working on right now, is IMO a recipe for a brittle swing that's liable to disappear at any moment. I'm also in the middle of major swing adjustments, so I've had to fight really hard on the course not to think about 5 different mechanical things over the ball. Just pick one thing to think about. If you start hooking it, pick the one swing thought or feel that most helps that miss, think of that, aim for the right side, and just try to stay athletic and play golf instead of playing swing mechanics.
For instance, in my round Thursday I was hitting the long clubs mostly pretty well but had so many holes where I'd pump a tee shot down the middle, have a nice short iron approach, then pull it way left of the green. Tried for a few holes your approach, lots of dry swings, mechanical thoughts, etc. Kept pulling them. By the end of the round I just was concentrating on one swing thought that's part of what usually helps me fix that in practice and started aiming almost to the right edge of the green (instead of more like right center, my standard aim point these days as my miss with the short irons is usually a pull right now). Hit the left side of a few greens that way. Frustrating but at least still a GIR.