When you want to cover up bad troubleshooting or bad operators, the finding offered to the management is always a loose wire. It cannot be refuted. Second place on hiding failures is the various assortment of blown fuses kept in the toolbox, where it is by slight of hand miraculously "discovered", while you fix the real problem.
Most modern controls systems today operate off of 24 volt wiring connected via ethernet signal, to a device specific controller that runs 460 volt AC servo drives, frequency drives, and hard contact motor starter relays. All it takes is an E-Stop bumped, a scan time error, or a button pushed at the wrong time, and it all shuts down.
There are no longer actual directly wired controls anymore. Everything operates with essentially phone calls at super high speeds in scan times. Every device shakes hands with every other related group device several hundred times a second. One hiccup in those handshakes not being sent or received within the prescribed milliseconds, and it all shuts down or pops up with errors which must be cleared with a laptop within the processors.
Not all technology advancements are the best for certain applications, but that's how we are rolling going into the future.