Z axis loses zero

Once I start the Gcode a tool change dialog comes up (not sure why).
After this dialogue it appears the Z axis is no longer zerod. If I attempt to use Touch Off, it does not put the Z axis to 0 but rather .6nnn . Oddly that .6nnn number it goes to is consistent and repeatable. To be clear, when the Touch Off dialogue appears, I do have 0.0 entered. But it does not actually zero the Z access post tool change dialogue. If I instead use the Tool Touch Off, I can zero the Z axis.

Any ideas what I am doing wrong here?

It sounds like you have a tool offset saved and your g-code is loading the tool and offset.

Would the offset be in the GCode or in LinuxCNC?

If you type in g49 in mdi what happens to the position readout?

It sounds like after the tool change completes it calls out g43 tool height offset

Here is outcome of checking g49 and g43.

1. Zeroed Z axis. DRO read 0. Loaded G-coded.
2. Started file (play button in UI).
3. Tool change dialogue appears. I choose okay (cause I do not need to change the bit...would love to get rid of this tool change)
4. Bit proceeds to dive into the work piece (3/4" wood) a 1/2". It should only be going in about an 1/8" (vcarve operation)
5. While at this too far plunged depth, G43 read 0.1595 (yeah it was well below this depth) and G49 read -0.4567 (more likely where the bit was at).

For step 5, I used MDI and the DRO with the program stopped and without moving the x,y,z axis.

Gcode that had run up to my stopping the program (using the Stop button in the UI):
%
(1001)
(T1 D=0.75 CR=0. TAPER=45DEG - ZMIN=-0.1427 - CHAMFER MILL)
N10 G90 G94 G17 G91.1
N15 G20
N20 G53 G0 Z0.
(ENGRAVE2)
N25 T1 M6
N30 S20000 M3
N35 G54
N40 M8
N45 G0 X1.087 Y-5.076
N50 G43 Z0.5 H1
N55 G0 Z0.2
N60 G1 Z0. F39.37

The Tool Table was the solution. In there I found the Z offset that keeping getting applied. Cleared it out, and things the two operations I did today went well.

Thank you.

I agree on the current and driver. I am working on upgrading from MyHobbyCNC driver to StepperOnline DM542T (outputs more current and higher torque) and a larger power source (34v to 48volts with respective current needs).

Thank you.