The height of the created image may vary

The problem should be with the machine and not the software.
Try the following:
In the “Move” window, give the command for the laser head to move 2 cm (or inches if that’s the case) vertically (Y axis) and confirm if the head actually moved 2 cm or something else. Repeat the process horizontally (X axis).
If the movement does not match the command, the problem is with the machine.