WooCommerce Ajax Cart Update Stopped Working

Question

I found a function to automatically update the cart when the quantity of an item is changed, and it was working until WooCommerce's 3.2.0 updated (latest update 3.2.1). I'm pretty sure something changed within this code:

add_action('woocommerce_cart_updated', 'wac_update');
function wac_update() {
    // is_wac_ajax: flag defined on wooajaxcart.js

    if ( !empty($_POST['is_wac_ajax'])) {
        $resp = array();
        $resp['update_label'] = __( 'Update Cart', 'woocommerce' );
        $resp['price'] = 0;

        // render the cart totals (cart-totals.php)
        ob_start();
        do_action( 'woocommerce_after_cart_table' );
        do_action( 'woocommerce_cart_collaterals' );
        do_action( 'woocommerce_after_cart' );
        $resp['html'] = ob_get_clean();

        // calculate the item price
        if ( !empty($_POST['cart_item_key']) ) {
            $items = WC()->cart->get_cart();
            $cart_item_key = $_POST['cart_item_key'];

            if ( array_key_exists($cart_item_key, $items)) {
                $cart_item = $items[$cart_item_key];
                $_product = apply_filters( 'woocommerce_cart_item_product', $cart_item['data'], $cart_item, $cart_item_key );
                $price = apply_filters( 'woocommerce_cart_item_subtotal', WC()->cart->get_product_subtotal( $_product, $cart_item['quantity'] ), $cart_item, $cart_item_key );
                $resp['price'] = $price;
            }
        }

        echo json_encode($resp);
        exit;
    }
}

My Javascript still working but here it is for a reference:

function refreshCart() {
    jQuery('.cart-builder .qty').on('change', function(){
        var form = jQuery(this).closest('form');

        // emulates button Update cart click
        jQuery("<input type='hidden' name='update_cart' id='update_cart' value='1'>").appendTo(form);

        // plugin flag
        jQuery("<input type='hidden' name='is_wac_ajax' id='is_wac_ajax' value='1'>").appendTo(form);

        var el_qty = jQuery(this);
        var matches = jQuery(this).attr('name').match(/cart\[(\w+)\]/);
        var cart_item_key = matches[1];
        form.append( jQuery("<input type='hidden' name='cart_item_key' id='cart_item_key'>").val(cart_item_key) );

        // get the form data before disable button...
        var formData = form.serialize();

        jQuery("input[name='update_cart']").val('Updating...').prop('disabled', true);

        jQuery.post( form.attr('action'), formData, function(resp) {
                // ajax response
                jQuery('.cart-collaterals').html(resp.html);

                el_qty.closest('.cart_item').find('.product-subtotal').html(resp.price);

                console.log(resp.test);

                jQuery('#update_cart').remove();
                jQuery('#is_wac_ajax').remove();
                jQuery('#cart_item_key').remove();

                jQuery("input[name='update_cart']").val(resp.update_label).prop('disabled', false);
            },
            'json'
        );
    });
}

I've been looking through the change log, https://github.com/woocommerce/woocommerce/blob/master/CHANGELOG.txt, but I can't find what would be conflicting now. Like I said, it was working perfectly before this updated.

Yes, I have a duplicate question here, https://stackoverflow.com/questions/46760969/woocommerce-ajax-cart-update-stopped-working, but I think I would get more help posting it in this channel.