[Quest Bug] Invaders

[P.A.T.Rick]

I already had problems at the start and probably missed the brawl between the kumans and the villagers. however, the current problem is more serious. after visiting the kuman camp. and the huddle with the nomad. the kumans have disappeared except for one guard. and have been sitting around in the tavern since then. i can't talk to any of them anymore and therefore can't complete the quest....
does anyone have any ideas on how to reset the quest? or what do i have to do? sleeping and so on has done nothing....

[McKoy]

I got the same bug, I got the quest going by speaking to Vasko, the one Cuman who knows how to speak in Henry's language. You have the option to ride to their camp to continue on the quest. He should be with the other 3 cumans huddle together at the tavern's table.

[Forlan]

Yes, but after that the quest is not proceeding. I mean after first drunk and helping one of them, they quest says return to Vasko. But he is on the tavern... And when i leave the camp it marks the quest failed, so i can only kill them to complete it. Have you faced such thing?

[FireHowl]

I have exactly same same problem. Does anybody knows how to fix it?