CMR, exhaustive or not?

In the (inter)national carriage by road the main obligation of the carrier is to deliver the goods in the same condition as in which he took receipt of these goods. Based on the articles 17 and 23 of the CMR convention , the carrier is liable for compensation when the goods are damaged or lost during the transport, or when they are delivered with delay. Any contractual stipulations which derogate from the CMR convention are null and void and impossible to enforce. It is possible that, besides this main obligation, it is agreed between the carrier and the shipper that the carrier will provide all sorts of other services. For example, arranging customs formalities, or providing information such as in which container a certain shipment has been stuffed/loaded. Some of these subsidiary obligations are governed by the CMR convention. The loss of customs documentation, as a consequence of which the shipper is unable to clear customs resulting in payable custom duties,  is for instance regulated in article 11 CMR convention. For a long time it has been uncertain under Dutch law, what the consequences are when other damage then damage to the goods arises under a contract of carriage which is subject to the CMR convention, with respect to a subsidiary obligation which is not regulated by the CMR convention. Is in that case the carrier liable for that damage (subject to national law), or is the carrier, based on the CMR-convention liable for damage/loss of the goods only?