Trading

So, I figured out how to set up a trade with an NPC ship, my half of the trade is loaded into the airlock, but nothing ever happens beyond that. Shuttle doesn't pick up/transfer supplies. NPC often ends up jumping out without the trade ever completing. Am I supposed to do something specific, or is this a bug?

I've found that if I explore the traders ship first, trade actions go off without a problem.  Be careful, though.  Pay attention to the faction of the ship before you try to board it.  I boarded a pirate faction ship thinking it was a trade vessel, and had to kill their crew.  Hope this helps!