The delay pretty much rules out a direct failure of the 12V battery itself. Probably also not the LI pack -> 12V charger hardware, I'd expect that'd be pretty easy to verify. Could be something software related on the later, though.
Once you get past the obvious and into software & electrical system at large working in the maze of a car's systems can be a real bear. Even with yesterday's cars. Especially here since this is a new system, so the tech involved will still be learning it here. There's training, and reading the nominal book, then there is working on the actual system that rolled off the line. Those are different in important ways.
The best thing one can do with a topic like this IMO is over-sharing, from that perspective. When there are first-hand views to the topic, there is less room for third-hand views.
