Good to know Eggs are still alive, is your temp in the incubator slightly low? that could be the factor for a slow development. A couple of years ago a friend’s incubator got unplug accidentally for a day that cause the chicks to hatch few days later than 21 days.
Yea my incubater was giving me trouble the first day or so, the temp and humidity were all over the place. Finally got it figured out and have another thermometer in the incubator to make sure everything stays correct.