I've been running my 3040 CNC for years without any major problems.
Lately, I've had to change the stepper driver, as one of the embedded one went bad. I used some TB6600. While doing this, I figured it might be a good occasion to replace the cables as they've been running for years.
I use Mach 3, and everything works fine. Ran a file and noticed that each pocket were not aligned. Ran the same file without material, and noticed the was something wrong with the X axis. After cutting, the router would not return to it's home position from the beginning. it was offset by about 21-22mm. It was pretty constant in terms of offset.
Did a lot of test: swapped the stepper driver, replaced them with some HY-DIV268, swapped the motor cables (new one have quick connect), swapped the pulse source being used, changed the motor. no matter what I would do, the x axis would always be offset. Compiled another file: same thing X axis is freakin' offset.
Watched it going: it would make its move then all sudden move quickly to the right or to the left, without any reason, out of the expected path.
I opened my file on some online G-code emulator: seems OK, as far as I can tell/see.
I'm stuck....Dunno what else to check. Only thing I haven't changed is the break out board for the pulses.
update: just noticed that when I operate the X axis manually, quite often, before going to the right, it will kick a few mm to the left, then start going to the right ...