Interesting: for me, the image quadrants display correctly in Safari, but there is a horizontal white line between the top and bottom left quadrants. You're not seeing that?

I see the white line on mobile, but not on desktop, though my OS versions are wildly different too, so hard to narrow down exactly what it might be there.

I see the white line on Safari, and also on Mac Firefox. No idea what the line means—it's not present in any of the reference images.

The white line is just because the four quadrants are four separate images, and the four images are HTML-aligned together to make one.