Same here.

Do you contact the customs office or the carrier first?

“Dispatched” means the label was printed. That is the entire meaning of the word. Currently on Deutsche Post myself.

Written confirmation email after every phone call. Cheapest insurance there is.

The sticker on the box is just so you know they were in there. It is the letter that matters.

Three month limits are cumulative across parcels in more places than people realise.

The declaration contradicting the return address is what gets it opened. Not on Deutsche Post but the pattern is familiar.

Photograph everything before you open it. Ten seconds, settles most disputes. Same for me with Deutsche Post, unfortunately.