Next time you incubate, you might want to turn your bator down a degree. Did you calibrate your thermometers? I calibrate to 100* by using a medical grade digital or old fashioned mercury thermometer in a cup of water at 100*. Then, based on that, I can pretty much tell how far off my other thermometers are. I am in the camp where I will assist with the occasional hatch. IMO, incubation is a substitute for a broody hen, and there is no way that I can be as successful. Sometimes, even if all incubator parameters are spot on, the chick can't make it out of the shell through no fault of her own. She may be so big that she can't get into position, If she can't get her head tucked under the correct wing (I believe it's the left) or if she can't get turned around so that she pips the correct end of the egg, then there's no way she can make it out of that shell. I've done assists where the poor chick had her head stuck between her legs, also where the chick was just too big.
I can't help you, but welcome to Maine, the way life should be!!!