Grunticon cannot read cssRules when using svgLoadedCORSCallback

I am using grunticon in an ember-cli project. I am using an external stylesheet for the icons so I have followed the docs to get SVG Embedding across domains working.

The embedding does work on the first page load but it stops working when changing routes. I found some help here where they suggested adding

grunticon.embedIcons(grunticon.getIcons(grunticon.getCSS(grunticon.href)))

to didTransition in router.js but the throws this error:

Failed to read the 'cssRules' property from 'CSSStyleSheet': Cannot access rules
    at Function.i [as getIcons]

This works if I am using the CSS locally but when I change to cross domain this is the result.