Issue with slider pulling dynamically

I'm having the weirdest issue and not sure where the problem lies.
On this page we have a post slider pulling 2 x slides dynamically from posts
https://zutari.thesandbox.co.za/expertise/roads/

When I go through the slides to the right (clicking on the triangle on the right), the one slide image doesn't show.

When I go through the slides to the left (by clicking on the triangle on the left), both slide images will show.

Very weird. Any ideas?