Unfortunately, this component does not work correctly now when you enable Experimental Lightbox[1] (enable experimental lightbox setting).
Whenever you have gate show when thumbnail clicked setting with experimental lightbox (which it seems soon to become default one), and click at thumbnail, the image will open in the lightbox successfully, while custom gate message will remain in the backrgound.
The solution is to not enable experimental lightbox for now. Hope this report helps updating the Component to properly catch new lightbox initialization.