Internal errors with crypto.subtle.importKey

Developers Workers
1

Here’s a fragment of my script that used to work.

  const Protector = {
    New: async () => {
        let keyPair = await crypto.subtle.generateKey(
          {name: 'ECDH', namedCurve: 'P-521'}, true, ['deriveBits']);
        return keyPair.publicKey
      },
    
    ToString: async (protector) => {
        return btoa(String.fromCharCode.apply(null, new Uint8Array(
          await crypto.subtle.exportKey('raw', protector))))
      },
    
    FromString: async (string) => {
        let buffer = new ArrayBuffer(133);
        let bytes = new Uint8Array(buffer);
        atob(string).split('').forEach(
          (char, index) => { bytes[index] = char.charCodeAt(0) });
        return await crypto.subtle.importKey('raw', buffer,
          {name: 'ECDH', namedCurve: 'P-521'}, false, [])
      },
    
    // ...
  }

Now if you do await Protector.FromString(await Protector.ToString(await Protector.New)) you’ll get an internal error with crypto.subtle.importKey. This started around 3 weeks ago (on or before 25 June 2022). Is this a bug or have I been doing something wrong?