Help needed! Z changes after touching the metal, to a value above the limits.

Hello, I have built a new plasma cutting table. I am working with Linuxccnc 2.9, Qtplasmac, and an LPT board. A problem has arisen: the torch touches the metal on the floating platform, the sensor is triggered, the Z value on the DRO suddenly changes by 100+, the machine goes into an emergency due to exceeding the Z‑axis limit, then the Z‑axis moves away and the readings return to normal. Please help me solve this problem.

Did you manage to fix this?
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We would need much more info about your setup, as that can be caused by incorrect settings in the ini file or by interference on the parallel port from touching material that is not in the same potential as the PC.

It wasn’t fully fixed, but there’s some progress. Now the machine finds metal and passes the test normally in the home position and if you only move the Y axis, but if you also move the X axis, the machine goes into error mode due to exceeding the Z limit. What information should be attached? I have a PC with an AMD Athlon 3000G, 8 GB of RAM, an LPT‑PCI‑e board, and an LPT‑mach3 board; it’s powered via USB from the same PC and from an external 24 V power supply. All the sensors are inductive, except for the metal detection sensor; there, an NPN inductive sensor is used, which activates a relay, and the signal is then sent to the board via the relay. The metal detection sensor does not touch the metal directly; it is mounted on a movable, spring‑loaded plastic platform, and when it shifts, the sensor is triggered.

GennadijSpb wrote:

... but if you also move the X axis, the machine goes into error mode due to exceeding the Z limit.

That does not seem right, and may be caused by errors in the hal/ini files, so upload the config files here.

I’m attaching the files.