I got a crash, and it's fully reproducible for me.

1. Go to Aureus, and get permission to visit the crime scene
2. Go to Town Hall, and collect Jahan
3. Go to the King's Crab Inn, and accept the Fabulous Five Quest
4. Add Madora to the party.
5. Go to the crime scene, and use Jahan's rain spell to put out the fire.
6. Get affected by the Stone, pick up the Love letter.
7. Take the entire party up the stairs, and try to go down again and the game crashes.

I did a little bit of testing, and the crash doesn't happen if at least one of your party has been disengaged and left downstairs. I'll have to reboot from earlier saves and test if the crash still occurs if I don't pick up everyone before visiting the crime scene.