Marketpress – category view pulling different products in

In category view, instead of just showing all the products in a category I have chosen, Marketpress seems to pull in an image from elsewhere and make the category link, link to that images product, if that makes sense.

For example, see here

Now, much as I like seeing my mug bandied around, it shouldn’t be at the top of there as it’s the thumbnail for an ebook I don’t have a cover from.

That page should list all the Twitter downloads (ones I’ve tagged with Twitter, including the one with the pic as the thumbnail).

If you look, ‘product category –> Twitter’ at the top doesn’t link to the category, it links to the ebook that thumbnail comes from.

What am I doing wrong?

If it helps, I’m using Genesis latest version with Serenity child theme.