I could confirm, that the trader is buggy. I used F5 for receiving the goods. I will try to do it via wholesaler and will inform in this thread afterwards.
Case was:
Do a place offer.
somebody else buy your goods
receiving of the goods are only working by pressing F5
not by using the trader itsself
Edit:
Already checked and it didn't work. In every case you have press F5, to receive goods.
I had to go to my offers to get the goods from an accepted offer.
It was already a pain to have to close and re-open the merchant, now it's getting tedious...
this is now fixed, and the good news is, you don't even have to open trader anymore or reload the game. You now get the goods of the trade as soon as someone accepts the trade.