Similar but different experience
Many years ago we had a rather similar thing happen. In this case the supervisor never read the messages, simply had a list of which Y and N to press in turn. Then one day an error message came up.
By the time we arrived the problem was fixed - because a new employee, a 17 year old girl, had wandered over, looked at the screen, read "Please shut the green door and press Y" and had done so.
I then had the pleasure of explaining to the manufacturing manager that instead of sacking her for "interfering with stuff that was none of her business", she should be marked for promotion. Years later this same young woman came up with a suggestion that nearly doubled the throughput of a section which had a severe production bottleneck - and again was attacked, this time by a middle aged woman supervisor.
Unions and traditional management - if a nail sticks up and is shiny, paint it black and bash it with a lump hammer.