When feeding FlatCAM output from GRBL_Laser preprocessor, GRBL complains about line “(Laser Power (Spindle Speed): 1000)”.
It seems that GRBL interprets first closing “)” as an end of a comment, and tries to parse “:1000)” into G-code, which fails.
I believe that the fix would be as easy as changing nested () into something else, e.g. .
Also, all these information comments could be replaced with to-line-end comments.