@xneera

I'm sorry that nothing seems to work. Didn't my instruction help you?
Yesterday I had another idea for a work around. Ubi says the bug depends on the world details but maybe on your computer specs as well, because on many computers the work around works but on many others it don't. Try and ask a friend if you can play on their computer / laptop with your save game. Maybe that could help. Don't forget to save after the bug.

@quackattack57

After two days of reading, searching and trying I FINALLY fixed it! Nothing worked but one thing did.
Careful: Do not touch anything when you reached the 2 hostages. You have to walk some meters towards them. The conversation won't start if you just enter the room and stay at the door.

I. What I have tried and DID NOT succeed

1. Start the game, change the setting to ultra high in the menu (!) not while gaming. The game restarted and I started the quest, didn't help.
2. Start the game, change the settings from ultra high to low in the menu. Restart. Didn't help.
3. Start the game, change the setting to ultra high again, restart. Changing the V Sync to adaptive. Didn't help.
4. Start the game as admin and done 1.-4. again. Didn't work.
5. Did 1.-4. in window mode. Didn't work.
6. Start the game, change in the menu the setting to low. CANCEL the restarting via task manager. Start the game as admin again. Didn't help.

II. What FINALLY helped:

1. Start the game, change in the menu the setting to from what ever to low. CANCEL the restarting via task manager. Start the game as admin again. Change low to medium. Restart the game. CANCEL the starting. Open the game as admin (!) from low to medium graphics (!) in window mode (!). Start the quest. It worked. If it works you'll see a video sequence after that the long house will changed inside and you can walk again. I'm so tired now that I can not play it until tomorrow night.

And don't forget to safe. Just in case of a freeze