Slick Slider sometimes works, sometimes doesn't

I'm using slick slider for a slider on a WP page template I built for a client, and I'm running into a problem where the slider sometimes initializes okay, and sometimes it doesn't initialize at all. I can't find a solution to why is it happening. When it doesn't initialize it just shows the slider content as full width images. Screenshots included.

This is how it looks when it's ok:

This is how it looks when it doesn't:

This is the slick slider code:

// Initialize slick slider
$('.sample-class').slick({
    slidesToShow: 8,
    slidesToScroll: 1,
    dots: false,
    arrows: true,
    infinite: true,
    autoplay : true,
    autoplaySpeed: 3000
});