We who build electronics, panels, complete airplanes, etc. are human.
I've been building for 45 years and do still make an occasional mistake.
The most recent was on a UAV that had about 1K connections.  Removable wings in 5 pieces, dual ailerons and flaps on each wing and dual controls on both ruddervators.  The one mistake that caused weird responses (all control surfaces would move randomly) was a simple polarity reversal on one connector to one aileron servo (the command line).  The tech and I wire checked it twice but due to an error on my part between two autocad drawings showing the same circuit, it happened.  The designer of the airframe, the newly assigned tech and an engineer spent days troubleshooting.  Finally one day after all of them had left, I disconnected all control surface command and power lines and tested them, adding one circuit at a time until I found the one which was causing the anomaly.  Upon verifying the pinout of the connectors going to it, I found the error.  Correct on one schematic and wrong on the other.  Since I was the one who designed the system and drew the schematics,  I was the one who made the error.  That proves I am human.
duane