Great video as always.
The 431 voltage reference would have been the last part I would habe checked. Quite unusual to see one fail.
If you still have the part, could you compare its behaviour to a new part? It could be interesting to see how it is different. Since the power supply was still in regulation, the 431 was not complete dead.
At the end of the video you made a mistake: You can not calculate the power consumption by only measuring the current, because all the filter caps in the power supply create a large reactive power.