There is no way for the output voltage to be 0 V when the external resistor is open.
The external resistance control of PWR-01 series is based on the external voltage control.
The reference voltage on pin 3 of the J1 connector is resistor-divided and connected to the voltage control pin on pin 1.
Therefore, if the resistor on the reference voltage is open, the output voltage may go to 0 V.
However, if the resistor on the COM is open, the output voltage may be at its maximum.
Please consider avoiding an open connection for the COM.