Need help with sudden lose of upward movement of Z axis during a cut

I am still learning all this... today i was surfacing a board, during the 3rd pass something failed, and the z aixs would only move in the down direction not up... I emergency stopped and started looking at what went wrong..

so i powered the system both computer and controller down and started checking, z axis would only move in down direction when i went to jog it..

i checked the config and nothing changed, i even tried to test move the z axis in the config and same thing only would move down..\

i changed the motor and same thing...

i turned everything off and cursed at it and put it in time out for about 15 min..

i went back out and plugged the z axis connector into the x axis to see if it would work, and sure enough it worked, so i plugged the x axis into the z axis and yup it worked both directions too.

i put everything back together and z axis is moving in both directions..

could someone point me to where i should check to see if it is possible what caused this.. just be for warned i am not really good with computers and even worse with Linux that controls my controller..

PS.. i was making deeper passes on the surfacing cut than i have ever done before, is it possible the system over heated?

Is this a pc computer issue or
A cnc controller issue???

I am using a probitix cnc controller and there pc system, it uses Ubuntu linuxcnc and no way of updating the system, it has no internet connection

I would check the cable to the Z dir on the driver for a break. If it happens again check the voltage on the dir connection when you jog it up and down as it should be about 5v in one direction and 0v in the other.

i checked the voltage as it was easier to get to, at the back if the computer i get 5 v in one direction and in the other direction it goes to 0..

i checked with the cable on to make sure no break in the cable and same reading..

so now i need to check the cable on the driver... i have been using the cnc for a couple of months now and never had a problem... the only thing i did different today was i was cutting at a deeper z depth when surfacing than i have ever done, i was cutting 1/8 and i could hear the router struggle with the 1 1/4 cutting bit.. could i have put to much pressure on the z axis and it over heated or just freaked out to hold the position

Maybe you fixed it when you unplugged and switched the z and x motor cables. I have found it isn't unusual for a plug to have a bad contact. You should check those plug contacts for signs of arking.

Again this forum and the experience here is great, thank you all for always helping out...

So i took the recommendations and dug into things on the cnc machine..

i checked the voltage and it was ok

The CNC Controller (probotix cnc controller) i have had this for several years, this is not a jab at them,, I went through all the wires in the controller and found not several but a lot of loose wires, I made sure they were tight and put it all back together..

then lastly because i have a probotix computer system also, and i had been trying to ad some programs to get a joystick to work, and thought maybe since its a closed system and no internet access maybe i downloaded something that was interfering..Probotix offers a download of a reload of ubuntu and it cleans everything else off..
i did the computer download and re configured Linux ..

i cut the same exact piece i was working on the other day when it failed, and no errors or fails today..

again thank you to all the help i get here.

That’s what I found, and I went through every wire and rechecked

consider the limit or home switch
as it blocks the movement towards home so up is blocked