I realize you are likely joking about the fire and this thread probably comes from a great place of frustration however selling a game to someone on here with full disclosure and getting anything out of them is better than creating a toxic mess in your backyard.
Now - removing all the mods and setting those on fire - I fully support that. Just because someone sticks a light bulb in something vaguely related to the pinball theme doesn't mean it belongs drawing power from your pinball machine via an alligator clip. Plus in this case it is a primary suspect for your problems.
I'm curious because your post wasn't clear - what was Stern's final conclusion? Did they say warranty expired? Did they just give up? Did they claim you voided it?