OS X CNA (Captive Network Assistant) doesn't l

Question

I wonder if anybody experienced this and, more importantly, found a solution.

In OS X (desktop) Captive Network Assistant doesn't apply CSS stylesheets for some websites including (at least) Facebook Login page:

Interestingly, it works fine on iOS devices – mobile CNA displays it just fine. Displays correctly in regular browsers on the same OS X desktop machine.

I would assume there is an error stopping it from loading stylesheets but since CNA doesn't have any debug panel or log – it's hard to say what is it.

I even tried loading a full React application in CNA and it worked fine so I assume that CNA limitations that some people discuss online are a myth.

Network issues are ruled out because Facebook hosts CSS on the same endpoint where the HTML is served from.