Straight Gallery Not Immediately Responsive

Hey there, I’ve just installed the Woo Shop Slider plugin, and I find it to be exactly what I would need. You can see my site’s front page has a slider – https://appareloflaughs.co.uk . The thing that I need help with is when the page loads the whole slider is taken up with one product image, but once I’ve moved around the window size, it suddenly clicks into place and becomes the slider that I would like it to be with the other products at either side.

Image of what its like on page load.

Image of slider after window size adjusted.

Any help would be greatly appreciated.

The page I need help with: [log in to see the link]