These eggs were old enough that they were putting off more heat than they required, so development was slowed but not stopped. So if for some reason your incubator has a problem and cools down for a period of time, don't worry. It probably will not adversely affect your hatch.
High temperatures in an incubator are an entirely different matter. Injury or death depends on how hot it gets and how long it is hot. Hot temperatures for brief periods usually cause no problem. But sustained higher temperatures allow the entire interior of the egg to become hot and that is when injury and death occurs. And if it is an older embryo, it is generating heat and this makes overheating even quicker.
There are no black and white limits with overheating. Years ago I lost all the eggs in an incubator when it was 105 degrees for six hours. But on another occasion, I had no losses when the incubator was 102 for four hours. An interior temperature of 103 almost guarantees death.
Just recently we had a machine that was supposed to be 98.7 gradually increase to 104 degrees over 3.5 hours. When it was discovered, we cooled the eggs as described below and the resulting hatch was completely normal. The eggs were 24 days old at the time.
What To Do When You Discover Your Hot Incubator
Immediately cool the eggs with water. If you have lots of eggs, spray with a garden sprayer or hose. If you have just a few eggs, dunk each egg in cool, not cold, water. Blow air over the eggs to more quickly cool them. Each time the egg dries, wet it again. Remember that as you cool the eggs, the shell will cool faster than the interior - but it is the embryo in the interior that must be cooled. Therefore, you want to cool the shell lower than the ideal temperature. And as I described above, don't be afraid of cooling them too much as temperatures below ideal will not be a problem.
If you have an infrared thermometer, I would cool the shell to 80-85 degrees. If you do not have a thermometer, hold it against your eye lid. Once it feels slightly cool, put it back in the incubator and turn it on (assuming you have fixed the problem in your incubator!).
Don't Give Up On The Eggs
Once you stabilize the temperature, wait a day and then candle the eggs. If they have died, you will know as there will be no movement and all blood veins will have disintegrated. Only then should you throw away your eggs. If you are not sure, leave the eggs in the incubator. You have little to lose keeping them in the incubator.
What experiences do you have after finding incubators colder or hotter than they should be?