I will try to explain the bug, with images, as briefly as possible (I have replicated the bug several times).
The Trading Post has two merchants, to the merchant 1 I am going to sell a merchandise (glassware) the merchant 2 is not interested, just when I am going to make the sale, the merchant 1 leaves, I make the sale and the glassware is assigned to the merchant 2 (let’s remember that he was not interested) he subtracts the gold, even when he did not have enough (he should leave it in negative).
The correct thing to do would be not to sell the item.
Mercader 2.
Mercader 1.
Sale. ¿?
Bug.