So it was because of this "East" and "Este" bug that I could not figure it out :) When at the mountain wall with huge closed stone door, you can select "East" and "Este". "East" will give you the GL264 code, while "Este" will make you go east. I thought it was a bug I got the GL264 code from the dome here also, but it was just the menu text that was wrong.
"East" should be corrected to "Examine inscription on stone door" and "Este" should be "East" instead.