I’ve been running into this periodically and think* it may be related to editing an existing Carbide Create file with different job info.
I did a Google search but couldn’t find anything addressing the issue on these forums and thought I’d chime in should it help someone else.
I opened the erroneous gcode file in ncviewer.com and removed all the ‘comments’ listed in green type within brackets and re-saved. It seems that the comments were throwing of CM’s ability to read the gcode… that’s my armchair analysis - worked for me with several ‘rogue’ files.
Hope this helps someone.