But did Boeing design those or was it outsourced far away ? There was an article on how they misdesigned the building system, it might have been a integration hell, reducing chances of thorough testing.

I don't know a single thing about this domain, but SpaceX embeds the same kind of batteries in a much larger and complex constraint space, it's another point for Musk POV.

Too bad Boeing and SpaceX didn't work together, it could have been a very synergic, local partnership.