For international shipments with customs declaration (CN23), only the first 6 order items are shown on the customs papers. Additional items are ignored.
Furthermore, only the total price of the first 6 items is shown. The merchandise value on the customs declaration differs from the actual value of the order.
Example customs declaration.
The order actually contained 7 items
with a total value of 1040 EUR.
The DHL Versenden API only takes the first 6 items into account. More item positions are not possible.
The problem is not caused by the Magento extension and can therefore not be resolved by it.
To prevent problems with customs, the shipment should always include a commercial invoice which shows all order items and the correct commercial value.
The problem is known to DHL. In the future, the API is going to show an error message if more than 6 items are in the package.