Duplicate items on product category page

So… this is a little bit odd, and I am hoping someone has seen this before or knows of a solution.

I have a woocomerce store : http://colinheaney.com

On the product category pagehttp://colinheaney.com/product-category/art-of-luxury/mini-kaftan/) when you click ‘More items’ it repeats some of the items.

As far as I can see this only happens in this category. I have checked the draft products and trash products but the back end shows that each kaftan is only in there once.

Any ideas?