Torchmate blue screen AVHC

I have been cutting parts out of 3/8" stl plates 5' x 10'
The cuts are long roughly 46" turn then come back 46" (guardrail posts)
I was using a HyperT 1650 machine with 60 amp tip set at 141 volts.
I noticed when the torch was traveling down the long straight cuts my cut voltage
would vary from 138 up to 143 then back down to 138 back up to 143, this cycle
was very consistent and took about a second and a half to two seconds.
I have a 10HP compressor with RTI filter then a MotorGuard filter and an AirGuardian
desiccant filter at the 1650, so I think I'm getting clean dry air. Machine is
not sloppy. Does anyone have any ideas what could cause this slight oscillation?
95% of the cuts were excellent cut quality with very easy to remove dross.
I forgot to mention I was using water about 1-1/2 to 2" below the plate.

Thanks in advance,
Mike Scalise
Deep South Texas

I'm just guessing but if it's not water in the air or an air pressure fluctuation issue, could it be a voltage issue to the plasma cutter? If not that haven't a clue unless it's possible variations in the metal which seems highly unlikely? Off the top of my head thinking that once the arc voltage changes it will obviously effect the torch height... which in turn will affect the arc voltage... which will effect the torch height and back and forth which may explain the back and forth between the two cut voltages you were receiving? Seems like the ATHC is not responding fast enough to keep a constant arc voltage setting. Strange they are consistent between those two voltages though, and 2 seconds seems like a long time for the ATHC to adjust the cut height. Is the switch set to "cut" and the voltage set to either 138 or 143? Is it changing as it passes over your table slats? Don't remember mine ever doing this, so interested in any additional findings.

This has me completely stumped. I called Torchmate tech support and the answer I got was 'it's the carbon in the steel'!
That's an answer I expect from people that hire people off the street for a tech job.
The slats aren't the problem as some of the long ways cuts were in between the slats.
I'm going to check for air leaks and I'll post a reply if that turns out to be the problem.
Thanks,
Mike S.

Good luck Mike!