Gap in background image on mobile, responsive design

[RayTracedObserver]

There is a large blue gap between the bottom of the portrait image of Ada Lovelace and the edge of the section or div on mobile devices. The gap is larger on a Google Pixel 6A on the latest version of Firefox than on iOS 16.7.8 iPhone 8 Safari, less large but still there.

It doesn't seem like there should be any gap at all. A gap makes no sense design wise.