Reported on Discord originally and was directed here by Putnam.

I can reproduce by sending the following squads out to raze a Goblin pit, and having them only bring back valuable treasure/release prisoners.
Walled Contingencies
The Gloved Plains
The Helmed Furnaces
The Glories of Steel
The Golden Eagles

I am not sure if the pit matters, but I sent them to one of the hostile ones to the south with plenty of books to recover. The game will crash when they return, a few moments after the notification pops up. Not sure if it's an item they recover or what, but I saw a few squad members come back onto the map before the game crashed.

I've attached the crash logs from my testing as well as the save.