"Well you see, making those conductors undersized saved us $1 per unit, which allowed us to get the lower bid, and increase shareholder value at the time. Now, of course, is a different financial quarter and what we did before doesn't matter."
I guarantee there's a spreadsheet at Ford that does the math on whether saving that $1 per unit is worth it considering the chance of a recall. Looks like their gamble didn't pay off.
The battery is fine, problem is the isolation contactors in the HV electricity distribution junction box. Contactors overheat, most likely melting their electromagnet windings. No more electromagnet pulling the contactor closed, springs push it open, isolating the battery as designed for a fail safe condition, no more power. Though the fail conditions are supposed to be "control system is not happy, cuts pilot voltage to contactors". Instead of the contactor itself being the failing part.
But hey still, atleast it's not welding the contactor closed, that would be way worse.