Homing Z direction Proforge 3

Last week I received the Proforge3 kit. I finished the assembly and I'm now trying to got through the programming. Unfortunately I'm stuck at the point of homing the Z-axis. At the start of the homing (Z) process, the printer head first goes to the Xmax and Ymax position (uppermost right and back position), but so far that the probe is out of reach of the bed and is not able any longer to detect the bed. The bed then firstly lowers and then goes up... but since the probe is not able to detect the bed, I have to perform an emergency stop by manually powering off the printer, otherwise the bed would push on the left ventilator of the head. Please, I need some help with this.