Gamepad buttons stop working in VR mode on Firefox for Android

When I switch to the VR mode on Firefox for Android and try to use the Gamepad keys, they don't work.
I use the Gamepad API with custom functions.
Everything works on PC in the normal and VR modes, and on Firefox Android in the normal mode. But as soon as I switch to the VR mode, the floor texture disappears, and the functions triggered by the Gamepad buttons stop working. I see that some buttons are triggered and could even see that some internal variables change. But the player is not moving.

Here are the error messages:
http://prnt.sc/12bwhr0
And this is what happens when I press the buttons on the Gamepad:
http://prnt.sc/12bwidm

I suspect it is somehow related to the ascene.js function:

function getCanvasSize (canvasEl, embedded, maxSize, isVR) {
  if (!canvasEl.parentElement) { return {height: 0, width: 0}; }
  if (embedded) {
    return {
      height: canvasEl.parentElement.offsetHeight,
      width: canvasEl.parentElement.offsetWidth
    };
  }
  return getMaxSize(maxSize, isVR);
}

But I don't see any values here, they are undefined. So, I don't even know if it is possible to debug.

I tried launching my page in Chrome for Android, but there, it is not even loaded.

As soon as I switch back to the normal mode, the buttons continue working.

• A-Frame Version: 1.2.0
• Platform / Device: Android 8.0, Firefox 88.1.1
• Reproducible Code Snippet or URL:
  http://localhost/aframe/virus_inspector/level2-xless.html

Reproduce the report with A-Frame 1.2.0 on Android 8.0 using Firefox 88.1.1 and the linked level2-xless.html example. Start by inspecting the reported ascene.js getCanvasSize function and the supplied error screenshots; done means Gamepad buttons continue moving the player and the floor texture remains visible after entering VR mode.