Revslider loading issue

I have an odd issue on my site where the revslider at the top of the homepage takes a split second longer than it should to load, and the result is that there are blank areas to the left and right of its colored background for a moment before it loads.

During a live chat, we tried overriding some elements with custom CSS, setting default width for desktop display in RevSlider to 1920px, and deactivating the SG Optimizer plugin, but just couldn’t get things quite right.

Can you have a look to see if you can spot what might be causing this? Thanks!