Depth testing issue where it shouldn't happen

Description of bug / unexpected behavior

An OpenGLLine and an OpenGLSurface don't work together as they should even though depth_test=True is passed to both.

Expected behavior

The green line in the example should be seen in total with the exception of the origin. When moving the camera around you can see other angles where the line is indeed completely above.

How to reproduce the issue

class SimpleSurface(Scene):
    def construct(self):
        frame = self.renderer.camera
        frame.set_euler_angles(theta=-30*DEGREES, phi=70*DEGREES)

        axes = ThreeDAxes()

        line = OpenGLLine(LEFT*5, RIGHT*5, depth_test=True)
        line2 = OpenGLLine(UP*5, DOWN*5, depth_test=True)#.shift(OUT*0.5)
        line2.set_stroke(color=GREEN, width=8)

        saddle = OpenGLSurface(
            lambda u,v: axes.c2p(
                u*np.cos(v),
                u*np.sin(v),
                0.2*u*u*np.cos(2*v)
            ),
            u_range=[0, 3],
            v_range=[0, 2*PI],
            color=BLUE_E,
            depth_test=True
        )

        saddle.mesh = OpenGLSurfaceMesh(saddle, depth_test=True)
        saddle.mesh.set_stroke(WHITE, 1, opacity=1)

        self.play(
            FadeIn(saddle),
            Create(saddle.mesh)
        )
        self.add(line, line2)
        self.interactive_embed()

System specifications

• OS: macOS Big Sur 11.4
• RAM: 8 GB 2133 MHz LPDDR3
• Python version (python/py/python3 --version): 3.9
• GPU: Intel Iris Plus Graphics 655 1536 MB

Start by running the provided SimpleSurface reproduction with OpenGLLine, OpenGLSurface, and OpenGLSurfaceMesh, then inspect how depth testing is handled in the OpenGL rendering path. Compare the rendered line and surface from multiple camera angles; done means the green line remains visible except at the origin when depth_test=True is used.