My thinking about the eggs that quit. I don't believe it was bacterial, no signs of it. But even though I only set the ones that were warm or cool, maybe they did get too cold before set. I did a bit of an experiment and put some in my freezer. When the eggs got close to the 39°-40° zone the yolk changed consistency when warmed back up. All membranes stayed intact and it wasn't a huge difference, but noticeable to the eye when cracked open. Maybe it degraded the cellular structure enough..... (Big guess only)
Moving on from that, I just set 3 eggs. 1 laid inside and 2 in the coop and were still warm and laid within the half hour. So they won't be part of this HAL, except to keep the other 2 eggs company!