If you have the Gigawatt slider enabled in Theme Options, you may see your images duplicated in the slider on posts where only one image should be. This is a problem with the WooCommerce product gallery including the image you set as featured.

The Solution

Edit the product post and check the Product Gallery meta box on the lower-right and remove the image by hovering over and clicking the X. The image should remain in the featured image panel. Click Update.