Egg hatching at 17 days?

[Quackter]

I have a chicken egg hatching at 17 days. Heard it piping, thought it was a duckling coming 2 days early, nope chicken egg. 21 days is Friday, temp is 99.5 by two thermometers. Anyone ever had this happen?

 

[FarmInProgress]

What’s your humidity at? That could be the reason, and try putting a kitchen thermometer in there to see if it’s actually 99... Some incubators 99 but are actually like at 101 Or 102 which makes them hatch early)but not in a good way)