Why do you see this typography when loading the web for the first time? And then it looks good

I have a problem with a web. In the first load, the navbar has a font family "A", but this typograhy don´t is the correct. When you do click in some part of menu and the web load again, you can see the typography "B". This typography is the correct, but I don´t Know the reason that happens. Can someone help me?

Really thank you very much!

The web with the problem

The web without the problem