It's NOT a fix but it's a workaround. Simply put, do NOT use 'DUPLICATE' image gallery. Instead, use 'ADD A SECTION' and start an image gallery from scratch. WHEN I duplicate an image gallery, the 'hide on' feature, although the image gallery indeed 'hides on mobile', for example, it still leaves the images showing up on the pop up/lightbox on mobile, thereby duplicating the number of images in the pop up/lightbox. I used to work at IBM and Oracle. When it came to quirks and quarks like this, we used to say 'it's not a bug, it's a FEATURE'.
