As to your statement as the problem lies betwen the keyboard and the chair since you had 20 years but in my working as a supervisor and manager for the city I have come accross people like you we called them know it alls. I just asked advice what could be causing it and you in turn decided just to put me
down. They tried to help with the rusting problem and even one admitted they have a problem with these from the supplier. It is the mold issue in 4 different humidifiers, the strange part it is always the one on the right I even replaced the left one just in case.