Must be a thing. Just got this low voltage error today. Car has not been driven in weeks. Noticed a car will not start error some time ago, which cleared. Then, high vampire drain and SMT showed the 12v being drained. Proactively changed the 12v, old battery tested and showed 33% loss of capacity. Everything was fine for a day, then the new batt started to get drained. Put it on a charger and still got errors, plus the low voltage, even though 12v on 10A charge, and 12.8v at the accessory socket.
Guessing the DC-DC converter is going which I guess means pulling the HV pack. Not happy on this low mileage, babied car.