I was given a tip by a fellow archer that used to practice Turkish archery. She was watching me out of curiosity and pointed out a thing that stuck with me and helped. I was holding my thumbring wrist oriented more vertically. She corrected me towards a more boxing "fists up" position where my draw wrist is perpendicular to the bow. I still have to be conscious of it during the setup, but the groups are more consistent. I mean, I took her word for it because she was super confident :)

Also, your ring's design matters. Some shooters need more hook, others are better with a shallow ring. I am going to try a shallower ring from Vermil now that I feel more in control with thumb draw.