#define DEFAULT_AXIS_STEPS_PER_UNIT { 10.616, 10.616, 5.308, 500 }
#define X_BED_SIZE 100
#define Y_BED_SIZE 100
#define Z_MAX_POS 100
If appears that you are working on something like a M3D Micro 3D Printer/Clone.
Could you post the location of the Z-Axis End-Stop switch and how it is wired NO/NC.