In my experience, issues with customs in Germany are VERY province-dependent.
A friend of mine stopped importing swords via his home City in North Rhine-Westphalia because of the constant issues with the customs officials there and now uses an address in another city instead. Same declerations, same categories, same paperwork - zero issues with the officials (so far).
I never had any problems in years, but was stopped, thoroughly searched and had my background checked by the border police at Hanover airport upon declaring my oversized box at the check-in counter (I had included the usual explenatory letter in the box, with my phone number etc.) three weeks ago.They were not unfriendly, but rather completely out of their depths of what to to now (and to do with me), continuing to call in the next level of authority. In the end they let me off the hook; however, it really took some time, friendliness / patience on my part and repeated explanations.
It is hit or miss, really.