I am not sure, but try to do so:
open file "modules/Wishlist/wishlist.php" and find next lines:
PHP Code:
if (!empty($active_modules['SnS_connector']))
func_generate_sns_action("AddToWishList");
func_header_location("cart.php?mode=wishlist");
and replace this code by this:
PHP Code:
if (!empty($active_modules['SnS_connector']))
func_generate_sns_action("AddToWishList");
func_header_location($_SERVER["HTTP_REFERER"]);
// func_header_location("cart.php?mode=wishlist");
After clicking on button "Add to wish list" the customer will stay on the this page.