In the PMDX-107 PDF, page 12. There is reference to deleting linearity.dat, depending on Mach3 version. I delete it, run the machine, linearity.dat is back, so is it safe to assume that's just the way Mach3 v_____.043.062 does it? So if you've EVER run the auto calibration, THAT messes up linearity.dat, but otherwise linearity.dat just lives there and gets saved seemingly every time Mach3 runs, looking at the file date. Everything seems fine, but I was just running thru my setup relearning stuff and ran on this in the PDF.
Curiosity killed the old guy!!!