Do you have Proxima Nova installed locally? The font stack does look for a locally installed version of the font first - it looks like it's applying the 900 font weight instead of 600.

I did. Seems that I had the regular weight and black version only. Disabled the "black" and it is rendering better now.

Looks amazing, once I fixed that issue.

Wow, that's strange! What are the machine/browser specs?