While playing through the Nightfall "The Lightblade" on hero difficulty. the trigger for gathering 2 orbs of power to move the boat did not behave properly and didn't trigger audio. As a result, the boat left while the internal flags for progress remained unchanged. causing a soft lock at the end of the strike were defeating the boss does not spawn the chest. Even if all checkpoints are hit afterward, the game will get stuck telling you to beat the Lightblade in order to progress. If you have already done so then finishing the strike becomes impossible.