Why it works: the argument that follows is not about judgement, it is about information, and everybody in it is being perfectly reasonable. That is what a handover failure actually feels like from the inside — which is why the people involved defend themselves so convincingly afterwards. A room that has felt this once recognises it in the wild.
Read the curtain out loud. It is the instruction that makes this work, and skipping it is the one way to break the activity.
Let them argue it out properly before you touch this button. The disagreement is the activity, and it will feel like a disagreement about judgement.