High squat mobility, poor control. This is more common in females, but also in males who've played sports that demand extra mobility as a kid, or who have a lot of congenital joint laxity.
For these people, they need to focus on trying to control the movement more, which means slowing down and thinking about positioning and trying not to bounce through the movement.
There's more to squatting than just getting under a heavy bar and popping a couple of blood vessels in your eye. Here are a few little-known variations of the king of lifts.