Yes, so if you are using individual redirects for each product, please make sure that you don't enter anything in the "thank you page HTML" field for each product as well as your account, so that the buyer is seamlessly sent to the redrection URL you have specified.
Also, please enable "auto redirect" and "payment data transfer" in your PayPal account. To enable "auto redirect", PayPal will ask you a URL (which we will override anyway) so you can simply enter your website URL there.