Flattening certain cubic béziers does not work about lyon HOT 9 CLOSED

#[test]
fn test_issue_19() {
    let mut tolerance = 0.0000001;
    while tolerance < 1.5 {
        let c1 = CubicBezierSegment {
            from: Point::new(11.71726, 9.07143),
            ctrl1: Point::new(-9.827381, 4.15774),
            ctrl2: Point::new(6.425594, 10.20536),
            to: Point::new(6.425594, 10.20536),
        };
        let iter_points: Vec<Point> = c1.flattening_iter(tolerance).collect();
        let mut builder_points = Vec::new();
        c1.flattened_for_each(tolerance, &mut|p|{ builder_points.push(p); });

        assert_approx_eq(&iter_points[..], &builder_points[..]);

        if iter_points.len() <= 1 {
            print!(" tolerance {}", tolerance);
            print!(" points {:?}", iter_points);
            panic!();
        }

        tolerance += 0.0000001;
    }
}

extern crate lyon_bezier;

use lyon_bezier::{CubicBezierSegment, Vec2};

const FLATTENING_TOLERANCE: f32 = 0.15;

fn main() {
    println!("Hello, world!");

    let segment1 = CubicBezierSegment {
        from: Vec2::new(11.71726, 9.07143),
        ctrl1: Vec2::new(1.889879,13.22917),
        ctrl2: Vec2::new(18.142855,19.27679),
        to: Vec2::new(18.142855,19.27679),
    };
    println!("\nSegment: {:?}", segment1);
    for point in segment1.flattening_iter(FLATTENING_TOLERANCE) {
        println!("Point: {:?}", point);
    }

    let segment2 = CubicBezierSegment {
        from: Vec2::new(11.71726, 9.07143),
        ctrl1: Vec2::new(1.889879,13.22917),
        ctrl2: Vec2::new(18.142855,19.27679),
        to: Vec2::new(18.142855,19.27678),
    };
    println!("\nSegment: {:?}", segment2);
    for point in segment2.flattening_iter(FLATTENING_TOLERANCE) {
        println!("Point: {:?}", point);
    }

}