Hi Hood,
Thanks for your response - Yes it is for no delay, or switching at the point of the axis movement, for a laser.
Funny enough the M10 /M11 combo also suffer similar, although slightly different, behavior. There is definitely something strange here as I have tried different computers with the same result.
I have attached a modified (m10/m11) version of the earlier GCode just in case anyone wants to see the difference.
Tweakie