So, Foot IK is the thing that makes the game change the position of the legs and feet so that they are always sitting properly if you are standing on uneven terrain. If one foot is on a curb while the other on the ground, it raises the foot on the curb by bending the knee. If one foot is on a surface not flat, it turns the ankle. You have to turn this function off for animations or else this happens because it is trying to make the foot level with the ground underneath it:     I spent