Main Menu flashes as plain text on first load for every page

Hi all,

My site is built with the divi theme, with plugins autoptimize and WP fastest cache to help with loading. Since I added a GA tracking code this problem of the main menu loading as plain text for a second before the rest of the site loads has happened, I’ve tested turning off plugins and removing the GA code but it’s still happening. Any help would be really appreciated, thanks.

The page I need help with: [log in to see the link]