A user reported the fault caused reboot using flash on the rpi forum.

We tested by ourself, the problem will caused by Xenon flash, which explains photoelectric effect.

Mr Upton admitted that he had not been aware that the Pi would be sensitive to camera flashes, but that he was not too upset about it.

sdr

Most cameraphone’s LED flash do not work, including nexus 5.

After the rough eye examine, the problem is caused by a DC to DC IC in this area

Screen Shot 2015-02-12 at 12.08.25 PM

More explains here:

It’s so interesting! You got a free thunderstorm sensor now. ^_^