z-axis end stop not working with Marlin on Prusa build

[Jared Nielsen]

Our z-axis end stop is not stopping when we send the extruder home. It keeps going until it mashes into the bed even after triggering the end stop.
It's not a connection issue. If we take the z-axis up and send it down 10 steps and midway trigger the end stop with a finger, the z-axis will stop.

We switched over from Sprinter & Skeinforge to Marlin & Slic3r and got one test print out of it. We changed the z-axis speed and started experiencing this issue.

[Nolan Poe]

Try rotating the endstop to change the part of the x carriage that it makes contact with. I've found that there are certain areas of the the X carriage that don't trigger the endstop properly.

[Joshua Wills]

Check to make sure the endstop is set correctly in firmware - if it's
set to home to min (Z-) but the endstop is set as a max, it will
exhibit some of the symptoms you report.