Butt winking, especially if you can squat fairly deep, is typically a motor control issue. Your breathing and bracing strategy my not be ideal and you may be trying to squat deeper than you need to with weight. Look back at the episodes Kaitlin suggested and take a look at your stance and depth. The human body, at the very end ranges of a squat, is meant to have a butt wink for pooping. If you are squatting with a bar (front, back, overhead, etc) you only need to break parallel so don’t chase depth you don’t have control over.