Probably massive subcontracting of software and digital design, mixed with supply chain issues, and unproven part substitutions at the component level.
Where are you seeing that this is battery related in the article?
The automaker's initial investigation showed the vehicles may contain a manufacturing defect that, "in heavy-duty cycle use conditions, can allow the drive pinion to cut its way through the outboard side of the drive-unit case," the filing with NHTSA said. The result could be an oil leak that can lead to an under-the-hood fire, the filing stated.