Aaah, plant shutdowns. I worked in IT in an automotive assembly plant at one point. Once, I was out on the plant floor with a colleague. We were diagnosing a new network drop and they plugged in a ping testing device into the cable, hit the button, and within seconds the entire assembly line went down. Cue lots of radio chatter and people driving up to us in their carts trying to figure out what was going on.

Turns out the ping testing device was last configured with the IP of a critical application server that talks to every device in the plant. When the colleague pressed the button, every plant device stopped contacting the apps server and the plant went down. Unplugging the device eventually fixed it. The line was stopped for 7 minutes. I believe stoppages were usually quoted at tens of thousands of dollars per minute and billed to the responsible department.

I remember how stressed everyone was after and meetings for root cause analysis in the following days. I was always surprised at this considering how frequently the line went down for small amounts of time, and they never seemed as big of a deal as that one specific time, though for the others we were not responsible.