Fraction bar goes invisible

Not sure if it is really a bug but when typing $$x_{\frac{2}{3}}$$ the fraction bar becomes invisible. It always occures when doing a Syntax note with a fraction. Without the fraction bar it looks like a binomial coefficient equation.

I can see it. Is it possibel that you have a low resolution screen? Can you try to zoom in or out?

Mhh, thats weird. Im using a 1080p screen and I am definetly not zoomed in/out. It looks like this on my PC:

I am having my Windows scaled on 125% (recommended), when I change it to 100% it works fine but thats way to small for me to work.