I had an Ebay shipment from the USA of a common Canon FD lens by a private seller with a 100% truly filled out USPS customs declaration. I was called to the german customs office where I had to open the parcel. The content was identical to what was stated in the form. But still german customs refrained from handing over the parcel, as they said that it lacked the required invoice inside the parcel. Never ever heard of such regulation. I explained that such would contain exactly the same data as shown on the form outside, except for the added term "invoice". No, the officer insisted on that invoice and gave me 5 days to present it. Of course the seller did not react on my request to send an invoice. Inspite of several visits during these days to the customs office, the parcel finally was due to be sent on my costs back to the USA, resulting in a total loss plus added two times shipping.
Sheer madness...
The respective customs office was located in a small 19th century harbour warehouse. The private shipments located in a small chickenwire cage in a dark filthy attic with birds flying along.... And only about 20 parcels, for a region of at least 1/2 million people....
But that is not the only mad encounter I had with german customs, threatened with totall loss of the goods.