Why can't I log in when I stand up from my chair?

A story about the 'unable to log in after starting up' phenomenon that occurred in the 1980s and early 1990s has been shared on the social message board Reddit.

The incident where the employee was unable to log in after starting up apparently occurred in a heavy machinery manufacturing plant in the 1980s and early 1990s. The modern factory had terminals on the floor connected to a mainframe for essential purposes, such as tracking parts.

One day, the system administrator received a call from a worker at the heavy machinery factory who said, 'I can't log in when I stand up.' The system administrator asked, 'Is the power on? What's displayed on the terminal? Have you forgotten your password?' The worker replied, 'I know what I'm doing. When I sit down, I can log in and everything works, but when I stand up, I can't log in.'

The system administrator explained that there was no connection between the chair and the terminal, so sitting or standing should not affect the login, but after a lengthy phone conversation, he finally gave up and went to the site.

The system administrator sat at a terminal, got the password from the user, successfully logged into the system, and then told the on-site technician, 'See? It worked. The password is fine.'

However, the person in charge replied, 'I told you, log out now, stand up, and try again.' So the system administrator followed the instructions and tried to log in while standing. However, even though he entered the same password, the message 'Invalid Password' was displayed.

The confused system administrator tried to log in with his mainframe account, but was met with an 'invalid password' message despite entering the correct password. He then sat down and entered his account information, which allowed him to log in successfully.

Hearing rumors that 'you can't log in if you stand up from your chair,' engineers working at nearby factories began gathering one after another to debug the issue. When the engineers all checked to see if their accounts were affected by the 'you can't log in if you stand up from your chair' issue, they found that a considerable number of people were unable to log in, whether they were standing or sitting.

After a lengthy debugging session, the cause was finally identified: someone had removed two keycaps from the keyboard and swapped them. The passwords of both the affected factory worker and the system administrator contained the characters from the swapped keycaps.

In other words, when sitting in a chair, the user was able to enter the password by touch typing without looking at the keyboard, which allowed the user to log in successfully. However, when standing, the user was unable to touch type due to the unusual posture, and had to type while looking at the letters on the keyboard, which resulted in the user pressing the wrong keys and failing to log in.

Comments on Reddit included, 'Seeing how the question was misdirected reminded me of one of my favorite stories,' and 'This is the best PEBCAK I've ever read.'