Hello,
There is a bug in the Fancybox Pro on Woocommerce galleries.
I checked it on a new installation of WordPress and Woocommerce.
No other modules have been installed.
A bug is when I launch the lightbox effect on the first photo, go to the last photo and exit the lightbox.
Then the thumbnails leading to bad pictures or no product image at all.
Regards,
Arek