Problems displaying objects in 3D scene

[1Dung]

Hi everyone,
I’m currently exploring 3D scenes in ManimGL.

In my scene below, I create a triangle and place spheres at the vertices and Line3D objects along the edges. Everything between the vertices and edges seems fine, but once I add object poly (with fill_opacity = 0.6) to the scene, it appears to cover or overlap the vertices and edges.

How can I fix this issue? Any help would be greatly appreciated.
Thanks in advance!

<img width="3840" height="2160" alt="Test3D" src="https://github.com/user-attachments/assets/29be7f2f-afe9-469f-bc1c-18220aefdd98" />

from manimlib import *
class Test3D(ThreeDScene):
    def construct(self):
        poly = Polygon([-3, 0, 0], [3, 0, 0], [0, 0, 2])
        poly.set_stroke(width=0)
        poly.set_fill(BLUE_E, opacity=0.6)
        verts = Group(
            *[
                Sphere(resolution=(51, 26), radius=0.2, color=RED_B).move_to(vert)
                for vert in poly.get_vertices()
            ]
        )
        edges = Group(
            *[
                Line3D(v1, v2, width=0.1, color=GREY_A)
                for v1, v2 in adjacent_pairs(poly.get_vertices())
            ]
        )
        ax = ThreeDAxes()
        self.add(ax, verts, edges, poly)