12/3 ecommerce quark quick install
www.ahgoobaby.com/Redesign3
VM action using the default template is to open related products in the same window. I just tried doing this on Quark and notice that it is opening on a new window in a separate tab. See: https://www.ahgoobaby.com/Redesign3/index.php/our-store/change/the-ark (scroll to bottom and click the changing pad cover as the visible related item).
I found a virtuemart forum post re-stating and advising the "product details template overrides need fixing. Compare the code with those of the default VM files in components/com_virtuemart/views/productdetails/tmpl/ - probably you need to look at default_relatedproducts.php"
Not sure if the above helps, but please advise how to get the related items links to open in the same browser window/tab instead of opening a new one.