Newbie here - why do I have engraving lines between my letters?

Hi, I have run this text 3 times and get these join lines in random places. I havent had this problem with other projects prior.
The text was a standard text/fill created directly in Lightburn, using a D1 Pro.

Check and see what your $32 is set to. It should be set to 1, i.e. $32=1 which will put it in laser mode. On a CNC machine it’s 0, so that the spindle doesn’t keep turning on and off.

Thanks Paul, machine settings tell me $32 is set onto laser mode.

And $31 is set to 0. Maybe upload file so we can look at it. This is only file doing this?

My apologies, at first glance I thought it was between each letter, but on closer inspection I see it’s only between some. If you do a preview with transitions on, do those lines show up? As Dskall says, if you could post the .lbrn file and a screen cap of the preview (with transitions on). It’s weird that it’s only between some letters.

So I ran another file which I use often, and the issue showed first time on this engrave. These are white cardstock, the joining line has shown up randomly on some and not others on the same page run, and in differing places … although always roughly the same top of letters. This is a different font to the previous example too, also created directly in LB. pic below.

I’m feeling suspicious about the cleaning of the laser head, would this do it? I wipe it down regularly with an iso-wipe however I keep thinking that resin buildup from the wood isnt being really removed well enough.
Also thanks for your help thus far!

Lens won’t cause this problem. What Lightburn version are you using?
If would enter $I then $$ in console and past results.

Latest version, it started prior to my recent upgrade though.