Pull-up resistor on Z-limit pin D11 isn't set correctly

[SimonGuethler]

Describe the bug

I've found the problem that the Arduino's internal pull-up resistor for the Z-limit is not set correctly. I've tested the Arduino Uno R3 by itself, meaning with an own script to set all Pull-ups, which works as expected. For some reason, grbl doesn't manage to set it correctly.

To Reproduce

Simply install grbl on an Arduino Uno R3 and measure the D11 pin's voltage compared to GND.

Expected behavior

As far as I read, grbl is expected to set pull-up resistors for all input pins per default. This works for the X and Y limits, but not for the Z-limit.