Shared link (slide view only) not rendering some icons

I use some Font Awesome icons in my prototypes, and it seems over the last week or 2 that they are rendered invisible in my prototype links to development. They are perfectly visible in my design document, they also appear in the small thumbnails when the link is shared in Slack, and in the grid view of all the artboards. The clickable slide view is the most important view for these to appear so my dev team builds these right, but that is the view with this problem... please help!

In my attached examples you can see a back button icon appear in 2 of the screenshots (link view / grid view), but not in the slide view