Large arrow briefly appears when loading pages

Hey there,

I am hoping somebody can advise me further. I have been trying to solve this issue, a large image (looks like a scroll down arrow) appears briefly in the header area when I load my site, and when I navigate between pages.

It does not appear every time and it disappears rather quickly, making it difficult to pinpoint, or inspect further.

I have managed to capture a couple of screenshots:
https://ibb.co/jVTZHXw

https://ibb.co/d2rRSgj

I would like to remove this from my site, as sometimes it appears on top of my header image and content and is the size of the entire screen.

Any help would be appreciated!

Thank you!

The page I need help with: [log in to see the link]