Solved desktop items loading on mobile

Static CSS File Cache should solve this issue:



But from what I see, you might've enabled it already, as I don't see any desktop items loading on mobile.

 

Upon further testing, I was able to see it. You might want to refer WP Rocket about it, their CSS file is loaded slightly slower on load.

You may try to disable WP Rocket & use the Divi Static CSS File & see how it goes.

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I also see that WP Rocket has a div: rocket-critical-css, which load the necessary CSS first, which you may consider to contact them on how they use it. For example, your fullwidth menu is showing up properly on first load, as it's using the rocket-critical-css