So I quicksave outside Neretaka, land at Neretaka and select Supply to gain access to the merchant. I open the Stash and dump a bunch of armor into the trade window. I then reload the game (F8) and land again at Neretaka and open the supply merchant - At this point all of the items that I had in the trade window are duplicated into my avatars inventory and I can sell them again. I do not enter the town, I do all of this from the map screen.
This does not happen if I open the inventory before landing at Neretaka, I have to land and open the supply to see the duplicated items. If I then leave the supply and go back to the world map, I can move all of the items from the character inventory into the stash, quicksave again, and then land at Neretaka, put the items from stash into the trade window and reload again for even more items...
I cannot attach the save file as it is larger than the allowed size even zipped.