JavaScript await not always working reliably on Firefox

I am experimenting with JavaScript’s async functions and the await keyword. I have created two promise functions to play an mp3 and to wait using setTimeout, and an async function to call them using the await keyword.

I was having trouble after playing a long mp3, and found that the same problem occurs if I wait too long. If I play a sound, wait for a while, then try to play a second sound, the second sound won’t play if the wait is too long, just under 3000 milliseconds. This is in Firefox, while Safari appears to be OK with this.

I have included a snippet, but the snippet works well, even in Firefox. I have included the same code online at https://resources.webcraft101.com/await-not-working.html and here it fails properly.

I cannot work out whether the problem lies with the function to play the sound, or something else.

 function wait(delay) {
  return new Promise(function(resolve,reject) {
   setTimeout(()=>{
    resolve();
   },delay);
  });
 };

 function playSound(sound) {
  return new Promise(function(resolve,reject) {
   var audio=new Audio(sound);
   audio.addEventListener('ended',()=>{
    resolve();
   });
   audio.play();
  });
 };
 async function playAsync() {
  await playSound('https://resources.webcraft101.com/sounds/drums.mp3');
  console.log('after drums');
  await wait(5000); // 2992 kills it
  console.log('after wait');
  await playSound('https://resources.webcraft101.com/sounds/cuckoo.mp3');
  console.log('after cuckoo');
 }
 document.querySelector('button#play-async').onclick=playAsync;

<button id="play-async">Async</button>