I am trying to use a KS0108 192x64 GLCD with openGLCD library. No matter what I do, the third chip is not being used. if I run the openGLCD\GLCDdiags, it shows it is using a 128x64 panel configuration in the serial monitor.
Sounds like you have not updated the library configuration for that panel.
See the openGLCD html library documentation for how to configure the library for a 192x64 panel.
See the section:
[openGLCD Graphical LCD Library]->[Configuration]