I think it might be because the water is cold, maybe try adding warm water instead. As the incubator warms up the percentage of the humidity will go down but technically it is the same as it was before, so when it says it is 70% humidity And 96f it might be the same or similar humidity as when...
So the temperature stays at 96f the entire time it is at 70-75% humidity? When temperature changes your percentage of humidity changes, so if you have 70% humidity and change the temperature the humidity percentage will change
It will only shrink wrap them if they have pipped. Does it go back to normal temperature quickly? What is the temperature before it drops or what temperature does it drop to?