Got the call last week that my replacement VCIM was in, and took it in today to be replaced. Things are working normally again. I asked what caused the issue, and the service writer said it was "probably a short" - he of course was unaware of any patterns with other owners. I specifically asked about the antenna and water intrusion, but he said it would be obvious with water leaking down from the headliner... Which I have not seen. Will keep an eye out, but for now at least the issue is fixed.