If these batteries have undergone third party testing by accredited test labs, it will be hard to prove the batteries are no good.
A third party report being presented is the opposite of immunity, it's an invitation to ask that third party some
very important questions. Their accreditation is on the line if things look amiss.
Even just showing the lab some internal photos might yield some interesting responses. Also you can ask them if they think their report is sufficient to prove the product as completely safe and reliable (they will
probably answer "no" for most product test reports, it is good to have this on the record for layman audiences).
In Australia at least many products must pass "all relevant standards" to be considered a safe for sale. Would a product like this meet insulation, fastening and fusing standards?