Can confirm, it's happened to me too. I'd expect them to drop their held items once they return home. But, here is how it happens:
1) Send pawns out on a caravan
2) They enter an encounter site
3) Tell them to manually pick up items off the ground, to be held in their inventory
4) Send them back to base via drop pods (haven't tried with a normal caravan)
5) The pawn will forever hold onto the items they took into inventory until manually told to drop it
Work around for now is to not pickup items with pawns, just load them into the pod via the load pod menu. This was as recent as version 1.1.2570.
1) Send pawns out on a caravan
2) They enter an encounter site
3) Tell them to manually pick up items off the ground, to be held in their inventory
4) Send them back to base via drop pods (haven't tried with a normal caravan)
5) The pawn will forever hold onto the items they took into inventory until manually told to drop it
Work around for now is to not pickup items with pawns, just load them into the pod via the load pod menu. This was as recent as version 1.1.2570.