Anybody consider as a separate issue that, as the car ages, coolant leaks are not all that uncommon... To have a battery cooling system design that allows leaking coolant to get onto a circuit board designed without adequate secondary circuit protection an issue all by itself.
Contaminants getting on circuit boards designed without regard to preventing escalation of failure to the point of fire has happened in a number of applications.
A number of home appliance fire issues are the result of similar failure mechanisms.. For example a widely sold dishwasher that had problems with leaks from the rinse agent reservoir leaking down onto a circuit board and starting a significant fire.. In the recall notice for this problem, it was documented that in this instance the fire accelerated to the point that houses were burned down..
Circuit board fires and design evaluation methods prevent (we called it secondary circuit protection) have been for a long time..
I would say Volt fires, (and applicance fire issues) raises the question as to how much analysis was done in the design phase to ensure such failure mechanisms were not in the design.
It doesn't take much imagination if you consider the resins commonly used in glass/epoxy circuit boards, types of components (e.g. carbon resistors, that when overloaded, can glow at red temperatures, and ABS plastics in the vicinity, that it all can become a nice smoke/fire initiator if protection is not inherent in the design.
Very briefly a design analysis/test cycle looks at the energy sources present and the components/mechanisms in the design to open circuit the failure following a time/current limit profiles well known in the industry to stop a short/low resistance failure from escalation to fire.
Analysis of the adjacent materials with regard to their ignition points and ability to contain a fire is another important aspect.
In a joint project with Motorola many years ago they introduced me to a process called "Failure Mode Effects Analysis"
Good practice to employ in any significant design venture, let alone one that uses new technology and your company/product reputation is at stake.