Creality Falcon works with Pass Through, but has double image otherwise

Scanner & Falcon Creality Falcon
1

My 10w Falcon works fine if I use pass-through mode, but creates a double image on all other modes, using LaserGrbl.

I have cleaned everywhere, checked screws, checked that it is square - all seem okay. Because the engraver works okay with pass-through (but not the others) I wonder if it is some setting in Lightburn? I have tried different speeds and different resolutions, but that makes no difference.

I have checked and as far as I can see the configuration is as per the pdf guidance.

Does anyone have any ideas?

Thanks

Well - no comments BUT. I switched off “Unidirectional Engraving” under “Raster Import” and the engraving worked fine. I suspect that the head is not firing to precisely the same position - 1-2 millimetres off on the Y-axis, so on the return it’s not pointing to the right place. I’ll give some more thought to this, but at least I have a workaround.

2

Is the line width (laser spot size) set correctly?
Are you in the Falcon FB group? They have example engravings (GCODE) to download, can you check this known working file and see if it turns out ok?