Just following instructions
One of my first jobs in IT (1980s) , was "application build". In those days DOS/VSE had one disk for the whole system!. Development tested on one system, I built on another system, and when the build was successful, switch disk, and re-ipl. So 2 disks in total.
I followed the instructions "delete the libraries using the ... command". 5 minutes later my manager came round saying the live system had gone AWOL.
I showed him the instructions and he said "ahhh. It should say use the build disk - see the white board, then delete the libraries".
I updated the doc.
Next week we had the same problem. My boss came in and said "you've messed it up again! Didnt you learn?" I showed him what I had done, and he said
"Ahhh, it should say update the white board to swap the disks round, then.."
Come the third week, I was in charge of a less critical build system.