Amplify Hub not firing on `auth` events. when running from Custom Domain

I have a custom domain purchased with Route 53. My Amplify app has hosting configured to use it in production. I can successfully login to my application from the backend https://prod.appID.amplifyapp.com/ domain. However, when I login attempt to login to https://myCustomDomain.org/ the Amplify Hub listener events never fire.

My app is configured like soo.

App.tsx snippet:

Amplify.configure(updatedAwsConfig); //aws.exports is updated to correctly set oath.redirectSignIn and oauth.redirectSignOut (per AWS docs)
console.log(`Setting Updated Oauth: ${JSON.stringify(updatedAwsConfig.oauth)}`);

Hub.listen('auth', authEventsProcessor);

function App() 
{ 
    //main app page is defined here.

authEventsProcessor definition

export const authEventsProcessor = (data: any) : HubCallback | LegacyCallback => {
//any => {
   console.log(`Processing Auth Event:\n${JSON.stringify(data)}`);
   //console.log(`Processing Auth Event(2):\n ${data}`);
   switch (data.payload.event) {
      case 'signIn':
      case 'cognitoHostedUI':
         console.log('signing in user');
         handleSignInEvent(data.payload.data);
         break;
      case 'signOut':
         handleSignOut();
         console.log('user signed out');
         break;
      /*
      case 'signUp':
         console.log('user signed up');
         break;
      case 'signIn_failure':
      case 'cognitoHostedUI_failure':
         console.log('user sign in failed');
         break;
      case 'configured':
         console.log('the Auth module is configured');
      */
   }
   return data;
};

pakage.json dependency snippet

    "@aws-amplify/core": "^5.8.6",
    "@aws-amplify/ui-react": "^5.3.2",
    "@aws-amplify/ui-react-storage": "^2.3.2",
    "aws-amplify": "^5.3.13",
    "react": "^18.2.0",
    "react-app-polyfill": "^3.0.0",
    "react-dom": "^18.2.0",
    "react-redux": "^8.0.4",
    "react-router-dom": "^6.4.1",
    "react-scripts": "5.0.1",
    "redux-saga": "^1.2.1",
    "tss-react": "^4.3.2",
    "typescript": "^4.8.4",

When I look in my Browser console I never see the 'Processing Auth Event:' line for my custom domain like I do for the amplifyApp.com domain. What's going on? Is this a bug in Amplify?