Reported as true story at my job (I was not there at the time, but shortly after, relata refero):
Rome 1990 World Football Championship.
A brand new telecom equipment installed at the stadium, tested, and perfectly working.
Then it started.
Every day, at approximately the same time, system failures with system restart (the expected down time should be less than 2.5 minutes/year).
The best technicians could not understand, until was discovered that tours with various countries' representatives were organized to show off the new equipment, and hence it also had a board on a board extender (to have it out of the rack, usually for debugging/test).
Some of them used a camera, with flash!
The flash was enough to have some diodes (in glass package) reverse conduct and bring down the system.