Torch Ignition and Crude Inside Nozzle

I've been doing a lot of running on just the pilot arc and some cutting with the torch too high. (I'm doing this to debug CNC interface software and get scope captures of the voltages.)

My torch stopped igniting, but had normal pilot arc voltage (around 62 volts). I switched from the CNC table torch to my hand torch and it arced properly.

After taking the nozzle apart on the CNC torch, I saw some "crud" from the electrode on the inside of the nozzle. It was easily removed with a small screwdriver. After that, the torch worked as expected.

Is the "crud" from extended operation on pilot arc only, or is it from cutting too high?

Thanks.