My Hats off to Sean for figuring that out…!!
Just confirmed it also. He’s correct.
With the tick box un-checked, sheetcam puts the S codes and (DTHC-on) and (DTHC-off) in the g-code on it’s own line.
When the tick box is checked, it reports the same, but wrongly puts the code on the same line as the x y move…
I say wrong… that combination just doesn’t work on our cpus for some reason. It must be working for other users…
Thanks guys for the help.
Aj