This has happened twice. I used pass without a trace to go near the druid grove, cut scene happens. I fought the goblins and beat them, but then shortly after the druids I just saved attack my group, it goes to a cut scene with the narrator saying "you wanted a fight now you've got one". I didn't pick up any stolen objects, I examined the goblins bodies. The second time I made sure pass without a trace was off. They attacked immediately after the goblin fight, didn't pick up anything this time, same cut scene.
Currently playing a tiefling paladin. Not sure if this would be a factor but I did get the flame sword from the killing the devil on the mindflayer ship.
