I use the RDC6685U controller, why are the cutting crosses not aligned?

Hello everyone! My CO2 visual cutting machine uses the RDC6685U control system, and in order to achieve accurate images, I specially performed cross correction. The parameters on the screen look normal and there are no errors in positioning. However, when the laser head moves along the trajectory of the material and the cross shape gradually forms, the horizontal and vertical lines do not perfectly overlap, the center point is significantly offset, and the lengths in the four directions are slightly different. Who can help me? esteem it  a favor.