I failed to mention that you will use a voltmeter to measure the voltage drop across the resistor.
In answer to your question -have we seen this before?- Yes, and it is just a matter of finding the source of the current and isolating the control circuit or filtering out the voltages.
One possibility is to get rid of the wires altogether and install a fiber optic line instead. But, that is a final and expensive but interference free solution.
