Thin white line between site header and Page Hero – how to remove it?

Hi,
I’m using GeneratePress Premium with a Page Hero (Header Element) on my single posts.
There is a thin white horizontal line appearing right between the dark site header (with logo and menu) and the Page Hero image below it.

I want to completely remove this white line.

When I try to remove it with CSS (border-bottom: none on .site-header), the Page Hero jumps up and sticks directly to the header with no gap at all. Changing margin-top or padding-top on .page-hero doesn’t help properly – the line either comes back or the whole thing shifts.

I just want the line gone and a small clean gap (around 10-20px) between the header bar and the image, without shifting the layout.

Any clean solution for this?
Thanks in advance!