We first started working with this site when the slideshow stopped working due to a highly customized theme and outdated jQuery. Full of complicated code, the old site was not responsive. The site is in the process of a complete redesign in 2018 using Elementor.
Prior to that, their old external gallery stopped working. We migrated their external gallery application into WordPress. We imported the gallery, created a custom gallery post type and used our new plugin, Featured Image Pro to display the images. We also created a gallery page that connected with the Picasa/Google Image API.