I simply DON'T KNOW!!! There is nothing in my comments that confirms that it is true.You can jump to your own desired conclusion thus assert as fact what you are suggesting hence lie as there is no evidence for it.
You do not consider or do not want to even contemplate issue being with gunpower composition being used for propellant.
You could have stated simply that maybe there was unburnt power and later on was ignited by howitzers next to it.
Also we can see gas from gunpowder exiting barrel normally as with others hence bore evacuator worked, or are you going to ignore that?
I only knew it "might" be an issue after reading Taepodong's post a few hours ago: