At once: I still couldn´t test a lot about the following issue, but it´s at least repeatable:
As we want to change herbs, my neighbour invited me to barter. Windows opened as it should an he put´s his offers in.
When i wanna do so, the first stack of Herbs worked fine, but with the second stack all my herbs (even the first stack) appeared back in my inventory.
Has anybody similar experience? I did not try other items - and by using the old-fashioned way for the trade, we didn´t also try if he´s got the same Problem when invited by me.