Thanks very much for all of your advice! It looks like this story now has a happy ending. I was finally able to explain the situation to Robert Melendez at LGChem, he was able to find a new installer in my area, Simply Solar. Within a week, LG was able to get a new battery to Simply Solar, and Jake Hassid and his team at Simply Solar were able to switch out the old battery for a new one, free of charge and without having to go through the warranty process. This really restored my faith in LG and their installation partners!