Custom css Flickering

Site URL: https://cod-smilodon-fkfw.squarespace.com/

I have attached an image below showing what flickers. Before the webpage loads, the portfolio flickers on screen for a second. Is there any way to hide this or allow the portfolio to fade-in with the global squarespace website fade in animations?

I am using custom css on the portfolio so this is most likely causing it but wondering if theres a way to hide and/or fade the load in. Any ideas?

The problem seems to go away when using Flex Site-wide animation. Could this be an issue with the site-wide animation conflicting with the portfolio?