Hi @Mcutewood - I believe that’s a bug from Bootstrap 4 beta 2 that was fixed in beta 3. Try using the final v4 release that just came out instead and see if that works for you.
And here’s an alternative way to use Bootstrap 4 in Sage 8 if you’re interested: Sage 8 legacy sites and Bootstrap 4 stable version. I think the main advantage over enqueuing the files directly would be if you either a) wanted it bundled with your other CSS/JS files or b) wanted to customize it for your site with SASS or including/excluding certain files.