Oh, try costume jewellery then, that seems to fly through with no problems at all, its the recommended NZ post description for jewellery without gold or precious gemstones like diamonds.
Don't you hate those officious types lol, I have one at our PO that I avoid, he always bumbles around and gets it wrong, takes forever to do the label and then says oh its too late they've just closed off labelling for overseas orders for the day. Duh grandpa, if you moved faster than a turtle we would have been in time.... grr.
On the bright side he's forgotten to charge me a few times for courier bags for my NZ sterling silversupplies orders, so hey, it all works out in the end. If he's really annoyed me, I forget to point it out to him!
Good luck with the tracking....