My 2 cents:
After reading the whole thread I conclude there just is not enough info to make any kind of assertion about what happened.
Several people pointed out the lack of BMS.... but was the system operated that way?
@Supervstech noted a bus-bar oddity that would be worth looking closely at, but we don't know if the system in the before pic was they way it was run.
All we can say for sure from the data we have is that there was a fire in a structure that had a lot of cells. For all we know the wood stove caused the fire and the electrical system had nothing to do with it.
The OP says it is not his set-up, and no one on the forum has claimed it was theirs so we can't even ask basic questions. All we can do is look at the ugly pictures and speculate......
And that is very unfortunate, if the system was involved in starting the fire, it would be an excellent opportunity for us all to learn and avoid similar mistakes.
If the OP could invite the owner to the forum to help us understand the event it would be very helpful. The owner can even set up an anonymous log-in to protect his identity if he/she is embarrassed by the event.