Geeetech

yes exactly.

The problem seems to be a faulty pin. Where can I find the h-Files for the firmware ?

actually the problem is even more strange.
I switched places of the end stop switch with the one of the Y axis. It turned out to work fine.

Then I switched the Y Axis end stop board-connection with the Z Axis end stop board-connection. It turned out that then the Y axis is lit all the time and ...

so, yes, this seem to be the problem. it's state is open all the time.
But I can't find the end stop for the A20T on the Geeetech page. They only sell the bigger red one. Where can I find this part ?

A20T

It is lit. It is red all the time and when something triggers it it gets a brighter red.

yes, it is 3D Touch and wiring seems okay.

here we go

Now it is different. The other axis seem to have problems too now.

https://streamable.com/mbipcr


The noise was the same for the Z axis, when using G28 command. When I used Simplyfy3D's JogMode to bring z to 0 there was no problems.

My Z axis endstop doesn‘t stop the z axis movement towards home anymore. If I home it I get a loud rattling noise. What are possible issues to look at and what codes are useful for debugging and posting the results here? Thanks!