For a client of mine we added bespoke Add to Cart buttons outside the loop. When a user added the item to their cart the parameter ‘add-to-cart’ still remained in the URL string. So when the updated their cart by adding or removing the product it would keep adding a single item back in.
The solution is to create a custom re-direct once a product has been added to the cart. This code could also be used to bypasss the cart and go straight to the checkout.
Solution:
Add the following to your theme's functions.php file
function redirect_add_product_to_cart() { // Custom URL return; // This links directly to your checkout page and bypasses the cart //return get_permalink( get_option('woocommerce_checkout_page_id') ); } add_filter( 'woocommerce_add_to_cart_redirect', 'redirect_add_product_to_cart' );