Issues with video feed (getUserMedia)

I have an iPhone 11 Pro Max running iOS14.2 and find that getUserMedia does not work in all scenarios. I set up my video feed as follows:

Code Block const setupCamera = async () => {
  if (!navigator.mediaDevices || !navigator.mediaDevices.getUserMedia) {
    throw new Error(
      'Browser API navigator.mediaDevices.getUserMedia not available');
  }
  const video = document.getElementById('video');
  const stream = await navigator.mediaDevices.getUserMedia({
    'audio': false,
    'video': {
      facingMode: 'environment',
      // TODO: Currently set to window.innerWidth and innerHeight elsewhere?
      width: undefined,
      height: undefined
    },
  });
  // console.log(stream);
  video.srcObject = stream;
  return new Promise((resolve) => {
    video.onloadedmetadata = () => {
      resolve(video);
    };
  });
}
const loadVideo = async () => {
  const video = await setupCamera();
  video.play();
  return video;
}

My HTML is:

Code Block 
<canvas id="videocanvas" width="100%" height="100%">
</canvas>
<video id="video"
       autoplay
       playsinline
       muted
       style="display:none"
       width='100%'>
</video>

I'm using three.js to render a video texture, but also find this problem is demonstrable without this (see the Tensorflow PoseNet demo here https://github.com/tensorflow/tfjs-models/tree/master/posenet).

The error displayed in the Javascript console for all of these is:

Code Block 
[Error] A MediaStreamTrack ended due to a capture failure
[Error] Unhandled Promise Rejection: Error: The video element has not loaded data yet. Please wait for `loadeddata` event on the <video> element.

However, the BlazeFace demo works (see https://github.com/tensorflow/tfjs-models/tree/master/blazeface) yet appears to function in exactly the same way as the PoseNet code.

I've tested this on 2 different iPhone 11s and an iPhone 12 mini with the same issues.

All of the above code works on iOS 13.5 on an iPhone X without any issues.

What has changed here between iOS 13.5 and iOS 14?