I just posted about mine spiking in temp and killing chicks that were inside drying off.
Everything was fine, all the eggs hatched except for one...and it was just a yoke when I opened it.
I cleaned it out and lowered the temp, put the chicks back in on some paper towels and went outside. I came back in and the chicks...except for 2 were all dead and the temp was 118 degrees.
I've had this incubator for years and never had a problem until today. I'm still sick to my stomach over it. I have never had that big of a spike in temp before today. All I can figure out is that it was some kind of a power surge, but I'll be leary of using it again.