Body Axis Angle When Crouching
Mechanism / Why It Happens
Once your body axis starts to lean during the crouching motion, the angle keeps increasing.
As expected, gravity always acts straight downward. If you crouch while your body axis is already leaning, gravity pulls you further in that direction, increasing the angle of the lean. This is why people often fall during the approach to a treflip.

What to Do
If your axis is straight, you won’t fall no matter how much you crouch.
Falling while crouching happens because your body axis is leaning. On the other hand, if you can <sp