Hello,
It looks that you did not read the full text of my last message.
2) Could you please provide us with a link to the product where you have the mentioned issue with the related products images and FTP access to your site?
3) Related Products is a section that pulls products from your store that share the same tags or categories as the current product, not just categories and it’s not related to theme but to WooCommerce plugin https://docs.woocommerce.com/document/related-products-up-sells-and-cross-sells/#section-3
Regards