I have also encountered something akin to this bug: In the Tomb of Xakoras, I destroyed the amphorae with a character in stealth. Then set a trap, then quicksaved. At that point Xakoras had not yet woken. When I loaded the saved game, he had risen but was non-aggro and untargetable, so the fight could not be triggered.
I think this may be a grammatical error for some of the dialogue with Himuihi. When she reacts to the player character being an Island Aumaua: “Hmph. As more outsiders pile in, sons the daughters of the tribes begin to look out”.