Emil_d08 on "Post thumbnails not showing"

I am having problem with this theme: https://wordpress.org/themes/store/. The blog posts images do not show as thumbnails on the home page, there are only place holders. If i add a separate image to blog post, using the 'featured image' option the image appear as thumbnail but also appear inside the blog post too, along with the original blog post image.
Any idea how to fix this?