I have encountered a similar problem, but haven't discovered a solution yet. I am using MACH3 with an ESS (AVID CNC) running on a W10 PC. My application is to use the CNC to conduct X-ray measurements on a surface and use G31 to set the vertical height before each measurement. My probe is a npn output from a laser displacement sensor and I occasionally had a crash that I first assumed was a sensor fault. To prevent damage, I added a limit switch which trips an ESTOP condition and halts all motion and execution if the probe operation goes too far. What I found is that the MACH3 diagnostics pane shows that the probe was sensed, but the Z axis was not stopped. In the most recent example, I had successfully probed a surface 995 times in succession without a problem before the crash occurred. On recovery, I verified that the probe worked by simply restarting the code and it was able to correctly probe the exact same location successfully and stop without error, and continue to work for hundreds more locations before crashing again. Since MACH3 does sense the trip of the probe, it must be a MACH3 issue,.. I think. I've tried to reduce the system overhead on the computer and disconnected the PC from the network, closed other apps, etc., but so far, the fault still occurs and is very random. There nothing special about the places where the faults occur. Hopefully, someone has an idea of what is causing this and suggest fixes.