I am not sure if this is considered a bug, but I doubt that the inconvenience is by design:

When a player receives multiple trade requests and start trading with one person, the trade request dialogue box remains there, and it is not possible for the player to communicate. This could be an issue if you need to answer certain enquiries or if the person you are trading with starts negotiating. Similarly, the same issue occurs if you have the Haven switching window open and receive a trade request then. You will be able to trade, but not chat.

This could be fixed by auto-hiding the trade request dialogue box as soon and auto-closing the Haven selection window as soon as one trade is taking place.