My site is based on the Flask tutorial and I'm having a problem that I don't see anyone else mentioning. After my site loads, the left half of the navigation bar "blinks" (disappears and then reappears) very quickly after the user clicks begins interacting with the site. This started right after I finished the tutorial and it's still happening today. Can someone explains what is causing this and how I can stop it? It happens with Chrome but it never in Firefox. Here's the site: https://sappho.pythonanywhere.com/