I'm bringing up my milling machine after replacing its ancient WinXP PC with a new Win10 one and a SmoothStepper. I thought I had everything dialed in, so I ran a program (admittedly a new one I'd never run before), and it stopped mysteriously about 85% of the way through (line 4990 out of 5660). I can't figure out why. I've attached a screenshot of Mach 3 showing the line it stopped on, a copy of the G code (generated by Cut2D from my drawing), and a photo of the part after the machine stopped (it was milling out that central pocket). Also, the spindle stopped gradually, like it was using Mach 3's deceleration parameter, not abruptly. Any ideas what's causing this?
PS - I realize the cutout profile should have been cut last, but in my zeal to get the program running I didn't realize I saved it in the wrong order. The tabs held everything together just fine, though.