I have a JCut 6090 with the Xulifeng Mach3 card (also called the Leafboy77 in some places). At random times a move will terminate before reaching the destination. The machine sits still for a period of time that is about what you'd expect for the move to complete, then starts moving on the next command. Of course, now it's in the wrong position, so the workpiece is wrecked. Sometimes when this happens you can restart the program and the problem occurs in the same place in the program. You can move the origin, rerun and encounter the error in the same place in the program, but a different physical position in machine space, suggesting the problem is not related to wiring and such. Also, if you reset the controller (by unplugging and plugging in the USB cable) the problem disappears. My best conjecture is that there is a firmware glitch that causes the current motion command to stop outputting steps. Note this is not a case of missing/skipping steps - the error is in inches, as much as 10" or so. Also, the motion is not continuous - the machine stops for several seconds, then starts up on the next command from Mach3. I've seen this occur within the first few commands of a program, or 15 minutes into a program. I've seen it occur all over the workspace of the machine.
Has anyone else encountered this? Found a solution? Found a way to contact the folks who make the board? I'd prefer not to have to replace the controller and rewire the machine, but...