Hey Jim,
“X” is not a valid address for G04 (Dwell) in the LinuxCNC and the Buildbotics G-code dialects. Try ‘G04 P100’ instead. Note that unlike historic CNC machines, LinuxCNC and Buildbotics assume the P value to be in seconds, not milliseconds.
Please be aware that running under 6,000 rpm is not recommended, especially on air-cooled, 24,000 rpm spindles (says my spindle manual)