This crash still happens. I reproduced it in a similar way as the orignal reporter. I'm not sure which of following steps are actually relevant, but here's what I did that lead to the crash:
- Joined an army
- Took a castle
- Took the Company of Trouble misssion from a fellow party leader in the Lord's Hall after the battle
- Left castle, re-joined army
- Spoke with a different party leader by selecting their icon in the army UI (lower right hand corner)
- Succeeded twice in the dialog options to sell the mercenaries.
- Game crashed
I uploaded my save file with a similar description to the link provided, but there doesn't seem to be any way to reference that after it's uploaded.
Also, leaving the army allows me to complete the quest by talking to one of the army party leaders.