First check with resistance meter with power off from common terminal to either side of the power in and to ground.
Next, power up and check ac voltage from any terminal to earth ground, you may see a reading with a high impedance meter, if you do see an odd reading, use a 1k -2k resistor from the terminal to ground, if the voltage collapses or reduces then it can be assumed that the voltage was due to leakage, reduce resistor value as necessary.
This test will tell if there is leakage that supports any kind of current.
I saw the mention of isolated I/O in one of the ACLenz description bulletins.
Nosmo.