It looks like the URL for that HREF is trying to load a page as a modal using the fancybox protocol. Is this what is expected?
Does that page ID exist? It looks URL looks different from the other page URLs on the site.
There is a jQuery function that targets every IMG tag w/ an A tag and applies a class of "fancybox". Modify the specificity of this function to exclude the last item in the gallery. Better yet, create a new class and add it to the elements that should have the fancybox functionality. The same issue happens on other pages where the HREF goes to a page instead of opening an image.
Current jQuery function:
var thumbnails = jQuery("a:has(img)").not(".nolightbox").filter( function() { return /\.(jpe?g|png|gif|bmp)$/i.test(jQuery(this).attr('href')) });
thumbnails.addClass("fancybox").attr("rel","fancybox").getTitle();