Sorry I just saw, that I overlook the "Z min" "Switch on GND, normally closed" configuration value in the online configurator.
Nevertheless it is not set approprieately after uploading an old Configuration.h Possibly in my case it wasn't read back, because I edited the file manually. Anyways this is a bit confusing behaviour. After uploading a changed file, the configurator sticks with a value magically stored in browser instead of reading the value from the uploaded config
So probably this is not a bug, but a bit annoying.