The thing I see in the VID compared to the Gcode is the Z axis direction may be backwards.

From the MDI line type

G91 {enter}
G1 Z1 F10 {enter}

DID the Z move UP or DOWN   It should have moved UP.

Just a thought, (;-) TP

well it has moved as it should for a few months.
Then this last week it decided that when you tell it to cut a pocket ot do a PVC project it wanted to plunge into the wood and drag across the material leaving a trough and then come up a bit and cut the edges like they should be.  Then the whole thing went to hell doing what ever it wanted.
Now I am back to just plunging and that is about all I can get because I don't want it cutting any holes in my work table, bench...floor...yard...

please try this simple exercise

From the MDI line type

G91 {enter}
G1 Z1 F10 {enter}

DID the Z move UP or DOWN ? 

(;-) TP

they do its a ESS http://warp9td.com/index.php/order   that's just one of them that can connect up with a G540

there are other ones available ever Ethernet or usb

I tried what you said.  The head went down

BR549 will comment this when he sees it.

If you started at "0" then the z axis should move up 1" as the code shows

Ray

BR549 will comment this when he sees it.

If you started at "0" then the z axis should move up 1" as the code shows

Ray

Is that up from machine coord or the zero I set?

IF you did the exercise as I suggested the head should move UP reguardless of anything else.

You would have set Mach3 to incremental movement(G91) and then MOVED in a positive Z  direction (UP).

IF it went down then there is your problem.

(;-)TP

then I have to ask...how could it changes it's own direction after working for weeks and weeks properly?

And why wont it hold calibration?