@Bruce
I believe it was Ozan who posted the image showing an LED in the stack unlit - certainly not me anyway.
I don't think we can attribute this to scanning/sweeping as that would be predictable and regular, no? What I'm seeing is completely random, like a child fooling around with a light switch. The intervals between breakdowns are completely arbitrary. I do like your final suggestion, though; must try that tomorrow...
Jinxie