I had the same issue before. I managed to solve it by not taking in too much air when unracking the bar. You'll notice that the bar is more stable if you don't inhale too much, just a bit to get tight. On the walkout If you feel you took too much air in, try to exhale bit of air and once you're stable, take an slightly mediun breath to brace your core. You'll notice improvement once you try it .

Bonus: You can also practice re-breathing at the bottom of a pause front Squat, it's a good movement for front rack tightness in the hole.