Did you get to the bottom of what you did? My theory.... On the assumptio n that the flashing light is saying that the hot water sensor has detected the water/ heat is too hot.... Did you fill the steam just before the incid ent? Maybe from a tap on the same mains cold water circuit as the inlet to the boiler? If so, my theory is that you turned the water on, it temporaril y starved the boiler of sufficient water throughput so it locked out for a period of time to cool down. The effect of this would not be felt by your wife until the hot water already in the pipe between boiler and shower is e xhausted and she gets the cold through....
Any good?