Hi Rich,

the hint with the xml-files was the key

I used an xml-beautifier and diff and then the rest was pretty easy. I don't know enuf to talk about reasons, but it looks like the default screen has an initialized parallel port and enabled axis, whereas my new scren had none of all.
I wonder, how mach3 did the green circles without any axis enabled

Anyway - I configured the parallel port and now my screen does the right moves too

But this leads to another "problem": I enabled the relais output for cooling and mist, but the buttons that should toggle cooling and mist did not work. I use LEDs with double-width grafics and those LEDs switch, when I issue an M7, M8 or M9 (in MDI-input) - but not, when I hit the button, that should toggle cooling or mist.
Is there another "hidden" feature I happen to miss?

M7, M8 or M9 (in MDI-input) - but not, when I hit the button, that should toggle cooling or mist

Compare the OEM button code used in  your modified screen  to the 1024 screen set buttons.

RICH

My gcode sample starts with this line: "G21 G90 G91.1 G64 G40"

G90 and G91.1 MUST be on separate lines if you want them to work reliably all of the time.

I'd have to check, but I believe that only the last one of the two is actually used when they are on the same line.

@Rich
I already did - and they are the same!

@ger21
cambam is quite heavily used by mach3 users - I can't imagine, that I'm the first, that run into trouble.
I'll keep it in mind and check for differences

cambam is quite heavily used by mach3 users - I can't imagine, that I'm the first, that run into trouble.

That's not specifically your issue. But it doesn't change the fact that the post is wrong for doing it that way.

And, if you only used CamBam, you'd never see an issue.
But if you were to run some G91 code before your CamBam code, you then run into an issue.

I wonder, how mach3 did the green circles without any axis enabled

You don't need any axis enabled to display the toolpath.

Oups - that's a bit to complicate for the moment.

I can not imagine a situation, where I want IJK be absolute, but I can imagine a situation, where I want G91 (instead of my default G90): when I raise Z to safety level. Not very common use-case, but ...
... so what is the right way to switch G90/G91 without changing G91.1?

Is it worth to raise a cambam-issue to change the mach3-postprocessor?

... so what is the right way to switch G90/G91 without changing G91.1?

As I said, they need to be on separate lines.