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

In the video you are approaching a pedestrian crossing next to a section of roadworks with red and white barriers; the traffic lights at the crossing show a flashing amber signal. Such a signal warns of an existing danger or traffic disruption. The answer is: yes.

The Regulation on road signs and signals states that a flashing or steady amber signal placed on an obstacle, or a flashing amber signal shown by traffic lights, warns of an existing danger or traffic disruption and requires particular caution. Flashing amber does not control traffic like ordinary traffic lights - it neither prohibits nor permits entry, it only tells you to be careful, and right of way comes from the signs and general rules. Before the crossing you slow down and give way to pedestrians, and near roadworks you expect a narrowed roadway, workers and machines.

Legal basis: § 98 para. 6 of the Regulation on road signs and signals; Art. 26 para. 1 of the Road Traffic Act (Prawo o ruchu drogowym)