Error 24 ( invalid gcode Id 24 )

Not sure why i am getting this error. Machine goes into Hold mode and runs fine after I hit resume. Using a spindle with the SLB on my Longmill Mk2 48x30. Using Aspire 12 for design. I did switch from grbl inch to grbl mm when saving and that seem to reduce frequency but it back today. Error 24 ( invalid gcode ID 24) I apologize in advance if this is not the right place to be asking this question, New to this.
Cheers

@Browner If you search on “error 24” on the forum, you will see similar posts and some solutions. In short, in not one of those posts was the gcode really the problem. I suggest that you see if any of the solutions resolve your problem, and if not, that you open a support ticket with sienci.