How "good" is the "X" display? Is it like a distorted Lissajous, or accurately formed? Can you move it around with the position controls? If it's well-made, and fixed at the center, then it's likely produced by the digital display system - maybe it's a fault indicator of some kind. The analog portion by itself should be incapable of drawing a good X, but the digital section can if it's somehow trying to tell you something. You may want to check the backup battery inside, and review the operating instructions to see if there is a meaning.
Ed
