36-70V stray voltage from switch box?
Digital multimeters, like older VTVM's, have very high input impedance and can measure tiny currents picked up through capacitance with an adjacent wire. Just touching one probe while grounding the other with a finger often shows such capacitive AC pickup. If that is the only source of the reading, then it's insignificant, not a safety issue. 

To confirm that there is no issue, put a 100 kΩ or so resistor across the probes to provide a small load (about 1 mA at 100 VAC) while measuring the voltage. Leakage of 1 mA would not be a shack hazard, but still should be less than a few volts.