Green Plane in Hello WebVR disappears in VR

[marcdownie]

Looking at the Hello WebVR example in VR makes the green plane below the sphere, cube and cylinder, disappear on iOS 14 (iPhone 12 and 8, WebGL 2 enabled or not, A-Frame 1.2 or 1.1, but not 1.0.4). Every time.

I don't believe that this is connected to ongoing view frustum culling issues in Three.js (where geometry disappears when it hits the top or bottom of the union frustum and never returns) because the green plane disappears even if I hit the scene graph with a:

AFRAME.scenes[0].object3D.traverse((node) => {
    node.frustumCulled=false ; console.log(node)
});

[marcdownie]

Curiously I can make the cube or the cylinder primitives on that screen disappear by shuffling the order -- the primitive last disappears (although it still casts a shadow on what remains). However, if I put the red sphere last I get:

(don't worry about the odd white frame here, that's just my iPhone 12 not being in the database)