Damage seems worse than at BOS. Even a terminal was burned off.
Failure scenario seems similar to BOS though. A cell short, over voltage on the other cells and then thermal runaway.
@RetiredF4
Frayed and broken earthing wire
Could be pre-existing, caused by intervention or a short to the case from a current source such as a cell shorting to its case. In case of short, I would expect more melting and burned insulation though.
If pre-existing, could cause floating battery case and (very remote) possibility of EMI disturbing BMU (the PCB's).