I can't help with the NEO motor issue, because that came along after I left Crown, but as for the brushes, I have found that you must replace them before you start getting motor fault codes. After you get the motor open codes there is no guarantee they will ever be right again.

I have cleaned up minor comm damage with modest success by using a very fine slender brush stone through the brush port. Physically disconnect the motor power leads, have the drive wheels jacked off the floor, and put it in push mode, then spin the drive wheel by hand to make the comm turn. It should only take a couple of spins to get the job done, then remove all the brushes and blow the motor out real good. I would only do this to a motor that has visible (light) comm damage. If it's heavy damage don't waste your time, just replace it. If changing the brushes before a fault has occurred, just blow it out.

Only OEM brushes should be used. The after market brushes have different brush cover caps, the lead is soldered on differently and the springs are lighter. I also think the brush material is harder. The OEM brushes are more silvery, the aftermarket are charcoal like

I'm going from memory on this part, so someone can correct me if I'm wrong. The new brushes straight out of the package are @ 14mm. The manual states the wear limit is 10mm measured length. A brush that appears to be only 50% worn is actually well past the limit.

The motors do get fairly hot when run on low brushes or with a weak set of batteries. Otherwise they run warm unless traveling on inclines or very long high speed distances.