The hazard analysis of lithium-ion batteries stems from the known chemistry and physical characteristics.
They can do, and do, go into thermal positive-feedback. This is physical fact. It is hard to arrest, and most airlines have no practices in place or equipment in the cabin to deal with it.
Given that the hazard is known, the relevant question is how it is mitigated in commercial aviation. Mostly, it seems people just hope it won't occur to them. The question of how many actual incidents have occurred is secondary.
PBL