Service worker does not load mp3 files

Question

Trying to load an mp3 file from the following source: https://static.twilio.com/libs/twiliojs/refs/82278dd/sounds/dtmf-1.mp3

Using very simple request redirecting code in service worker:

function onFetch(event) {
    if (event.request.url.indexOf('.mp3') >= 0) {
        event.respondWith(fetch(event.request.url, {mode: 'no-cors'}));
    } else {
        event.respondWith(fetch(event.request));
    }
}

have tried other options as well:

fetch(event.request)

fetch(event.request.url)

fetch(event.request.url, {mode: 'cors'})

note: no error thrown in service worker if I pass {mode: 'no-cors'}, error thrown for all other mentioned cases:

Fetch API cannot load https://static.twilio.com/libs/twiliojs/refs/82278dd/sounds/dtmf-1.mp3. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'my origin' is therefore not allowed access.

I think the issue may be is that Service Worker does not send Accept-Encoding and Range Headers, so it does not load the resource.

Any kind of help, hacking would be appreciated.