So here's the deal:

I'm pretty much brand new on this Thermwood Machine, and am using artcam as my toolpath program. I'm looking to run multiple rounded rectangles out of a 1.5" board of mdf.

My daylight values are not accurate and my spoilboard is screwed to my table board, along with the inability to flycut an uneven table, so i have modified my gcode the artcam produces a bit so i get the results i want. I have the z-shift to adjust for this, along with giving me the ability to aircut to test the program. I've run a couple of test programs and the other day i was cutting a similar program completely fine.

Today i adjusted the toolpaths for a 1.5" board of mdf with a ramp in and 2 passes. I thought i set it up correctly and sent the file to the machine, but when i ran the part, it gets to the line after M31 and just stops dead. Spindle and all. No E-stop, no error message, just stops.

Is there some conflicting code in my file? I've compared it to other files and it seems to be similar, no noticeable differences or wonky commands.

So what's my problem?
Here are the lines of code leading up to the problem:
(Program Name-florsheim)
M999
G90
G92X.5Y-12.25 F200
SET ZSHIFT=3
T1 M3
S15000
(0.500 inches dia. slot drill)
G00 Z3.0000
G01 X0.2500 Y12.0000
M31
G00 X0.2999 Y1.1397 Z2.0000
G01 Z0.2500 F200.0