MathJax (external JS library) not being loaded

Following my recent issue with the nonce error, I tried loading MathJax from a CDN instead of having it in the directory locally. Good news: I do not get that "forbidden nonce" error anymore: Bad news: I have to refresh the site about a dozen times to occasionally see the effects of MathJax. Most of the time the blog displays the ugly commands instead of transforming them into mathematical symbols.

I get "\frac{dx}{dt}" instead of the symbols.

Furthermore it seems that the blog likes to eat the markdown signs. Instead of ##Headline2 I will sometimes have #Headline2 but sometimes the Headline2 is still in its original size as it should be, not as Headline1 as one would expect.

Could those two issues be related? The engines eats format commands and MathJax then finds nothing to layout correctly?