And backup your data, just in case. Those hard drives don't always transfer very nicely.
My guess is the light flicker was just enough for something to turn off the "power good" signal from the supply, which tripped some sort of protection circuit. After things cooled down, it was good to go again.
Don't know if this will be helpful, but here's a power supply circuit diagram for one of the power supplies. Maybe we'll get lucky and it'll match your model.
https://www.minuszerodegrees.net/5160/psu/5160_psu_schematic.htm
Oh that's neat! That schematic shows the expected wave forms at certain points.