Hero video: background color shown between fallback image and hero video on load

Hi there,

I have a one-page website with a lot of (panorama) images and hero video (loop). On load there is a fallback image first, then flash of white background and then video. Is it possible to eliminate the moment of white background, please? Or any idea how to fix it?
The website url see below.

I followed the https://docs.generatepress.com/article/page-hero-background-video/.

Thank you