Frequent "A network error (such as timeout, interrupted connection or unreachable host) has occurred." with Firebase

I'm using Firebase anon login to authenticate certain parts of our API. This error "A network error (such as timeout, interrupted connection or unreachable host) has occurred." seems to pop up frequently with no apparent pattern.

This seems to happen in all types of browsers. Mobile, tablet or desktop but I can't for the life of me reproduce this error. I've tried many different types of physical devices as well as Browserstack.

Some have suggested that users experiencing this aren't allowing Javascript or have some kind of browser extension preventing Firebase to work correctly. I find that hard to believe since this keeps happening very frequently. (Also I've never met a person in my whole career that has Javascript disabled).

I initialize Firebase like so in my React's index entry point.

if (!firebase.apps.length) {
    // ... config setup
    firebase.initializeApp(config);
}

firebase.auth().signInAnonymously()
    .catch((error) => {
        bugsnag.notify(error);
});

I'm using React 16.8.6 and Firebase 5.9.4.

Error seems to be originating in google-closure-library:

../node_modules/google-closure-library/closure/goog/async/nexttick.js:41:44

from Frequent "A network error (such as timeout, interrupted connection or unreachable host) has occurred." with Firebase