Material Icons and Roboto not loaded in Safari - only Safari

You seem to be running into exactly the bug you've updated your post with.

Are you perhaps redirecting the user a bunch of times on initial app load? If so the safest bet would be to wait for actual user input before starting any redirects, this will also ensure everything has been loaded properly.

An alternative approach would be to wait for the document to become ready via (i.e. jQuery's) document.ready function:

$(document).ready(function() {
    // your code here
});

You could try putting your code there or, alternatively, wait for user input until initiating the redirects. I personally didn't have any luck with the document.ready approach and switched to the user input method.