Woocommerce variation images not changing

Hi there,

We're having issues where the featured product image doesn't change when clicking the swatch.

I understand this was an issue with one of the woocommerce updates, but we've updated to the latest version (3.5.1) and it's still not working.

We have a customised single-product file, but we've replaced this with the standard wc template and it still isn't working.

We've tried deactivating conflicting plugins but can't seem to come to a solution. I just wondered if anyone has experienced the same problem and found a solution?

Any help/advice is much appreciated!

You can see an example product here: http://www.fryetts.co.uk/product/narvik/