Hi @rouvers ,
Did you mean the list of custom related products in the Related products tab of the single product page’s Product Data? Could you kindly make a screen recording for me to get your issue?
You can go to WPClever >> Related Products >> check if have enabled the Defaut related products: https://prnt.sc/k2B_CzmFASR5. This might add default related products to all products on your site.
You can also check it by deactivating any caching plugin on your site to make sure the changes can be saved and updated properly.
Best regards.