Why are not all items added to the cart?

Question

WooCommerce

$(".tocart").on( "click", function() {
var cart_date = $('.sbor .tocart').attr("data-cart").split(';');
cart_date.forEach(function(item, i, cart_date) {
  product = item.split(',');
  varid=product[2];
  qty=product[1];
var data = {
    action: 'my_action',
        product_id: product[0],
        qty : qty,
    variable_id: varid ,
    };
    jQuery.post( myajax.url, data, function(response) {
    });
});
});

add_action('wp_ajax_my_action', 'my_action_callback');
add_action('wp_ajax_nopriv_my_action', 'my_action_callback');
function my_action_callback() {
   $product_id= intval( $_POST['product_id'] );
   $qty= intval( $_POST['qty'] );
   $variable_id= intval( $_POST['variable_id'] );
   global $woocommerce;
   $woocommerce->cart->add_to_cart($product_id, $qty, $variable_id);
   wp_die(); 
}

Here is the main code responsible for ajax adding items to the cart, everything works well for 1 item, that is, everything is added well in one addition.
and when there are already several goods and the forEach loop is triggered, then the goods disappear, out of 5, let's say 2 are added, in random order. from woocommerce doesn't seem to notice
Yes, I need to add several products at once.

Answer 1

Woocommerce makes checks before adding to the cart and in case of an error it fills in the notification. Then he displays these messages to the user.
Your code is ignoring this.
Check the messages, maybe they have the answer.
Look at the native add-to-cart code.