Hi there,
In the single product page we find the following:
1. Gallery seems to be an image behind when viewing the array of product photos in the gallery. ie. When you click the image to look at it in the main view, it shows the image afterwards.
1.a. We did use a ‘Twist’ plugin which works better but then includes the product image as well as the gallery images which throws everything out of line because the product images are all portrait and gallery is all landscape.
2. When you click on the main image to enlarge it in the lightbox, it then does show the product image with the gallery images, so maybe there is some coding somewhere which is ignoring that portrait product image from the gallery but is having an effect with the synchronising between seeing what you are clicking in the gallery (before expanding the lightbox).