[Slider] Slide not loading all slides

We’re having the same issue but strangely we have two almost identical sliders and one of them is playing and the other is stuck on the first slide (unless you refresh the page).

The images are defined as the background of the slide, rather than an image added to the slide, or within a div inside the slide.

Any idea what is causing this? The image circled on the left side is the one that doesnt play.