Traders/wanderers dropping items when they agree to join your kingdom or completing trade

I've had a fair few cases where I've traded for items, and the traders drop it onto the ground, where it spoils before any of my nobles can pick it up. 
Might be an issue with me organising job hierarchy, but it still feels like there could be a better way to handle it.
(Maybe the ability to allocate an area for trade items to be placed?)

Possibly related;
As far as I can tell, every noble that agrees to join my kingdom will drop whatever they're carrying the moment they say yes. Instead of adding their supplies to my stockpiles, they will just leave any excess on the ground, and I have to scramble to control my ruler/assign everyone to hauling to make sure it all gets brought inside before anything is spoiled.