In Google Chrome:
If I add data-modal-mobile-target="..." to grouped images, with the first call, (on a mobile device) it opens the lightbox. Then pressing the arrow, it shows the mobile target (so just the picture).
In Firefox it works as expected ans opens just the image and then one has to go back.
Also in Chrome I get a warning in the console: [Violation] Added non-passive event listener to a scroll-blocking 'touchstart' event. I think its related, but my javascript knowledge is limited and I was not successful fixing it...