The IT unit at a school has new wiring (1 year old) and on one work station bench there are about 12 or so computers and monitors all powered the same ring circuit.
Each double socket powers one computer and its associated monitor.
It has been discovered that when you unplug or plug in a monitor that sometimes some of the other monitors (either to the left or right of the monitor that is been plugged and unplugged) lose their display for a few seconds.
I have checked the circuit and it is fine.
One other bit of info. The slower you plug or unplug the monitor seems to make this happen more often.
I can go back in for another look if anyone wants any more info. My job was only to confirm that the circuit was safe but I like a mystery.
 So the school closed the IT room for H&S reasons.