Main Image appears below correct location after thumbnail is clicked

hey, first great plug-in its exactly what I wanted. I am having one problem that I can’t seem to find a reason why it happens or a solution. Each time I click the thumbnail image to have it appear as my main image, the new main appears below where it should before snapping into place.
Here is a link that will show you what I mean: https://gordonchrystal.com/projects/16-henrietta-street/

How do I stop it appearing below before snapping into place. I wish for the image to appear at the top once the thumbnail is clicked.