I wonder if Boeing EE's are tracing the route of electrons from the ground power receptacle throughout the aircraft to see how current could leak into the ELT circuit. Let us suppose that they find something that allows a stray voltage to wander here or there. Hmmm.
I bet they are! I'm not familiar with this kit but, given I understand it is not powered from any aircraft bus, I would have expected any external control wires to be galvanically isolated from the ELT electronics via an opto or something, so there should be no possibility of any sneak back-feeds, but you never know, I have had someone tell me in the past "I don't need to isolation from the system, it's battery powered". Only true if the number of wires connected is equal to or less than one I think!
I presume it has an external antenna? I hope nobody did a bad thing with antenna grounding.