In this situation, does the flashing light warn about a danger or a traffic disruption?

Yes, a flashing yellow light warns of a danger or traffic obstruction. It means that the traffic lights are not operating in their normal mode (red-amber-green) and you must exercise particular caution. In such a situation, the driver is obliged to obey the road signs that determine the right of way, or in their absence, the general rules of the road.