Still barking up the wrong tree
The fact that there is a measurement of 20 Volts per metre does not mean that the voltage will be developed across a coil. The problem is that the relay coil has a very low impedance compared to air, even looking like a short circuit. There is no way a PED would create a field strong enough to drive the current.
Sorry, it is out of the question.
If a PED had interfered with the high-impedance parts of a circuit that controlled a relay, then I could see it, but by the fact that we are talking about relays acting on their own I assume that has been ruled out