I’m able to reproduce this not just in LightBurn but in a few other applications as well with the same font (I’ve realized now it’s just a standard windows font).
The problem is likely that, because it’s a script font, the lines are very close together and as far as I can tell this is a problem with the underlying framework we use and not any specific LightBurn code.
Granted, there’s a much better way to do script fonts now and that is single line (SHX) fonts:
https://lightburnsoftware.github.io/NewDocs/FontsAndText.html#shx-fonts
There’s a few forum posts already where people have posted collections of SHX fonts you can download, like this:
Using these fonts would likely make for a cleaner burn as it won’t have doubled up lines like the the font you are currently using.