I'm going to continue beating this dead battery.
So, I agree that the fire most likely happened from heat at the terminal.
The reason I think that is because it is obvious from the picture that the main intensity of the fire is centered around that terminal.
Just for reference, my short was on the top side of the busbar and it still melted the terminal and busbar.
But lets just say fhorst's short was at the terminal or below the terminal.
fhorst said his terminal was lowered a small amount.
He thought it was from kneeling on the wood resting on the stud. That might be the cause or it might not.
I assume it would take quite a bit of weight to actually push the terminal down. Especially with all those busbars.
His studs are so long it probably would tip easier than push the terminal down.
It is possible the terminal just lowered because of the heat. Heat tends to distort most things.
People really want to come up with a quick determination and blame fhorst so they don't have to worry that this might happen to them.
That is the easiest.
I'm not easily convinced. There still are multiple possibilities.