I am working on a large laser picture 52"x29" that the gcode file has over 807 million lines (including comments). After etching 359 million lines, I had a network error that stopped the machine. I have not been able to determine why the network error since the machine is isolated and I have implemented all of the PC setup steps. Anyway, I restarted the file (it takes a little over an hour to load) and that process missed the gcode line F 250, that sets the laser motion to 250 inches per minute. This caused the laser to slow down in certain sections over cooking the etch. To recover I made another gcode file that included the correct preamble with the F 250 command that started on the last xy line where the initial error occurred. This worked fine.
So I thiink that there is a problem with restart not including the F xxx commands.