Hello Roberto, I did a general maintenance on my printer (I washed all the plastic casing and sponges from the trash) and went back ... the care I had with the transparent disk, searching the internet, was to place the small marking (colored square) exactly in the position of the sensor ... that's right, inside the sensor, as accurate as possible, but still, my pages are about 2mm wrong, but it's already something. I did not open it again to fix it, but I believe the position is not totally wrong.