The following snippet works in Chrome:

(async () => {
  var i = document.createElement('iframe');
  document.body.appendChild(i);
  var a = i.contentWindow.eval('(async () => await 1)');
  i.remove(); // someone removes the iframe
  const v = await a();
  console.log(v);
})();

Our use case has code that works when wired up and then someone removes the iframe and `await` no longer resolves.