I don't much about the G100, but sounds like you are having noise issues causing communication errors.
Try running the Gcode file without the steppers or spindle running and see if you get less errors.
A high frequency spindle will mess up any system that is not properly wired with huge amounts of noise.
Are you grounding the G100 to the chassis and using a 3 prong plug with the same ground tpo the computer ? Or are you grounding the controller chassis to the cnc machine in any way (It shouldn't be ). Ethernet is not opto isolated and you don't want current flowing through the computer and controller ground.
Remember, the people who developed Ethernet and USB, didn't know anything about the noisy CNC environment ! Old RS232 was running at +- 15 volts to reject noise. USB runs at 3.3 volts and Ethernet at 5 volts