Recently my laser starts to cut twice (retrace?) when I am sure it is just one simple hairline shape such as a circle. I use Illustrator 2018 to make the shape, and then open Lightburn to import the ai file. I have a Chinese CO2 100W machine. I don’t think I had this problem before until recently. I don’t think I updates any software.
I’ve had just that situation, where AI creates two copies, one of which has a rectangle (bounding box?) as part of the second copy. It makes it easy to delete the ghost, as you find the rectangle, click on it and the second image goes too.