By default the fixed header height in Divi shrinks down the menu and logo when you start scrolling down the page. This makes the header more compact. If you or your client don’t like this effect than you can disable this from happening. You only have to make one very simple adjustment.
Stop the Divi header from shrinking down on scroll
In your WordPress dashboard go to:
Go to Divi > Theme Customizer > Header & Navigation > Fixed Navigation Settings
Change the fixed menu height value to the same value as in the menu height settings:
Divi > Theme Customizer > Header & Navigation > Primary Menu Bar
When you scroll down the page the fixed header will remain the same size.
Check out my other Divi theme logo tutorials