WooCommerce Booking & Appointment Plugin: wrong price on cart and checkout page

The site I am developing is using the WooCommerce Booking & Appointment Plugin (http://www.tychesoftwares.com/store/premium-plugins/woocommerce-booking-plugin), I create a custom form to add mutiple products to cart at one time. Here is the code:

function booking_add_to_cart() {
    if ($_POST && is_post_type_archive('product')) {
        global $woocommerce;
        if(is_array($_POST['qty']) && !empty($_POST['qty'])) {
            $woocommerce->cart->empty_cart(); //Clear the cart

            foreach ($_POST['qty'] as $product_id => $qty) {
                $qty = intval($qty);
                $product_id = intval($product_id);
                if ($qty > 0 && $product_id > 0) {  
                    $woocommerce->cart->add_to_cart($product_id, $qty); // Add product to cart individually.                                    
                }
            }

            $checkout_url = $woocommerce->cart->get_checkout_url();
            wp_redirect( $checkout_url ); //Redirect to checkout page
        }
    }
}
add_action( 'template_redirect', 'booking_add_to_cart');

But there are something wrong with the prices on checkout page. Some of them are correct and some aren’t.

The plugin is using three filters to modify the prices:

add_filter('woocommerce_add_cart_item_data', array('bkap_cart', 'bkap_add_cart_item_data'), 25, 2);
                add_filter('woocommerce_get_cart_item_from_session', array('bkap_cart', 'bkap_get_cart_item_from_session'), 25, 2);
                add_filter( 'woocommerce_get_item_data', array('bkap_cart', 'bkap_get_item_data_booking'), 25, 2 );

However it’s not working correctly in the custom form I created. Can anyone help me with this? Thanks in advance.