Hi Bdice!
The links on the gallery images are wrapped around the actual image object itself and the caption markup is included in a different page element. Overlaying the caption on the image covers up part of the link area, which is why only the top half is clickable after making your customizations to the caption positioning.
You should be able to make the entire area clickable by removing the ‘collision detection’ for captions by adding an additional custom CSS rule. Try adding pointer-events: none;
to your CSS that repositions the captions over the gallery images. That solution worked for me in my own testing and I hope you have the same success with it!
Please let us know if you ever have any other questions for us in the future!