Just to throw in another Monkey Wrench on this topic. I constantly have this problem where the security station stops working because it is missing one or two security guards, but there are about 50 sitting in a staff room about 20 feet away. Specifically with security this happens to me a lot - and it happens in baggage security as well. The red indicator say that it needs more staff to operate, but I have never figured out how to get them there.
It happens MORE frequently when there a tons of people in the queue to the station, when the airport is empty- it rarely happens.