From the quick look at your profile info and the likelihood of coming over from CNC I’m guessing the setting for spindle mode is on which is marking the traverse lines with your laser.
While connected to the engraver, In the Console window in LightBurn please request the settings report from your engraver by typing the following:
$$
then press Enter.
Please copy and paste that report into a reply here.
I’m suspecting $32 is the setting that has gone awry.