.auth0.com/oauth/token 504 Gateway Timeout only on OSX Safari

Using Safari Version 14.1.1 (16611. on Mac OSX 11.4 (20F71) when my Angular SPA POSTs to oauth/token during login Safari is reporting 504 Gateway Timeout.

The error only occurs when the POST occurs from the service worker on the SSL enabled site. Running debug or production builds locally works without error.

On the same laptop using Chrome, Firefox, or Brave the same application logs in the same user without errors in dev and via https. Safari on iOS also logs in correctly.

Any ideas?

In case anyone else come across this, there is this open issue against Angular that describes this scenario along with a potential work around: service-worker(safari): POST requests getting blocked with 504 by Service Worker · Issue #37133 · angular/angular · GitHub

It would be helpful if Auth0 developers could advise on how to correctly configure an Angular 10+ PWA using a service worker to login to Auth0 in desktop Safari.