Post edited. Originally, the bold word was Liability!!!
It's hard to call it quits when there is still a chance of viability. At this point, that's doubtful. But, this is what I'd do: carefully, remove each egg one at a time. Give it a sniff test. Candle it, looking for signs of life. Tap on the shell and cluck at it. Best to do this when there are no witnesses. I've been called crazy for doing less certifiable things before. If no audible signs of life, you can do a float test. I honestly have very little faith in the float test, but... you have nothing to loose. Finally, if no signs of life, carefully open the air cell, again checking for signs of life. Do not break the membrane until you are certain the chick is dead. Then you can do an eggtopsy to see if you can determine cause of death. With this many failures, I would do so.
Or. You can unplug the bator, bury the eggs in the garden, then sterilize the bator. You might want to check your thermometer calibration since you got hatches on day 19.
