I just fixed it using the selectors. You have to be super careful how you paste the shortcode though – I copied&pasted from a text editor and it messed it up. Even the quotation mark ” seems to be of importance (low, high).
[image class=”video-1″ src=”image-1.jpg” link=”true” href=”//www.youtube.com/embed/kfVsfOSbJY0″ lightbox_video=”true”]
[lightbox selector=”.video-1″]
[image class=”video-2″ src=”image-2.jpg” link=”true” href=”//www.youtube.com/embed/kfVsfOSbJY0″ lightbox_video=”true”]
[lightbox selector=”.video-2″]
[image class=”video-3″ src=”image-3.jpg” link=”true” href=”//www.youtube.com/embed/kfVsfOSbJY0″ lightbox_video=”true”]
[lightbox selector=”.video-3″]
etc.