Again Marco, a grain focuser that isn't set to one of your eyes specific vision, with or without corrective lenses is worse than useless, as you have already demonstrated.

Assuming the mirrors haven't been replaced, knocked out of position, the crosshair is in the factory aligned position, the frame isn't otherwise bent, spindled or mutilated, the optical adjustment to the user's eye is just plain off unless the user has uncorrected astigmatism when using the grain focuser