Visual bug in the raytracer?

I do not know if this is a bug or normal behavior, but I am confused by an elongated object in the reflection of a red sphere, what is it?

My scene:

s = Scene(
    [
        Light(
            type_=LightType.ambient, 
            intensity=vec3(0.2, 0.2, 0.2)
        ),
        Light(
            type_=LightType.point, 
            intensity=vec3(0.6, 0.6, 0.6), 
            position=vec3(2, 1, 0)
        ),
        Light(
            type_=LightType.directional,
            intensity=vec3(0.2, 0.2, 0.2), 
            direction=-vec3(1, 4, 4)
        ),
    ],
    [
        Triangle(vec3(-1.5, 0.5, 5.2), vec3(1.5, 0.5, 5.2), vec3(-1.5, 2, 4), vec3(0, 0, 0), 500, 1),
        Triangle(vec3(1.5, 0.5, 5.2), vec3(1.5, 2, 4), vec3(-1.5, 2, 4), vec3(0, 0, 0), 500, 1),
        Sphere(
            color=u8vec3(255, 0, 0), 
            radius=1, 
            center=vec3(0, -1, 3),
            specular=500,
            reflective = 0.2
        ),
        Sphere(
            color=u8vec3(0, 0, 255), 
            radius=1, 
            center=vec3(2, 0, 4),
            specular=500,
            reflective=0.3
        ),
        Sphere(
            color=u8vec3(0, 255, 0), 
            radius=1, 
            center=vec3(-2, 0, 4),
            specular=10,
            reflective=0.4 
        ),
        Sphere(
            color=u8vec3(255, 255, 0), 
            radius=5000, 
            center=vec3(0, -5001, 0),
            specular=1000,
            reflective=0.5
        )
    ]
)

full code is here: https://github.com/linux-admin0001/raytracer