Wow! Amazing how the slightest touch does it for this old cloth wiring. However, had these not been disturbed, the signals could have gone on for years before a short developed. Eventually it would have happened though. I find this in old fluorescent lights from the 40s all the time. Usually the wiring is brittle near the ballast because the heat is generated the most from there. Sometimes the rest of the cloth wiring is OK but if the light was in a harsh environment the whole length of wire is often stiff and breaks like uncooked spaghetti.
Thats exactly what was going on here. I have two other signals with cloth wiring in much better shape. The condition of the wiring was likely a contender in getting both of these replaced