The source of noise is 100% the spindle, I have been running for months already with a porter cable router and have had no noise issues as far as i can tell. When I run the spindle and send step/direction signals to the servos, axis position "grows" due to noise being perceived as step pulses. However, the machine is working totally fine despite the EMI spewing spindle when I use the 5V USB connection or a non grounded walwart supply. I have tested the repeat-ability for over 30 minutes at different spindle rates and it is solid. As soon as I introduce earth gnd to kflop GND I get rogue steps.