Could the Beacon Be a Red Herring?
A heck of a coincidence, but maybe, the beacon wires were already burned, from the first time it was powered up, and the fire in question, just happened to be in the proximity of the beacon, so the investigators saw it and said "Well, there's your problem right there!" I've seen this a lot, troubleshooting electrical, electronic, and other technical problems, over the years. People assume that the first problem they see is the problem they are looking for, but it turns out to be unrelated. Wonder if there's a way to test, with some precision, "how fresh" the burned wire insulation is?