Yes you will loose them using the incubator as well. To be honest the whole incubation process can be stressful, but there is nothing more heartbreaking to me then to have a chick fully develop and then for one reason or another not make it through the hatching process. So many things can go wrong and with some of them there is nothing you can do to prevent it. I've had experienced hens accidently step on the eggs mid hatch and squish the chicks trying to adjust them underneath her. I've also had one try to make that external pip into the yolk sack and that one ended very badly. Then there are the ones that completely develop and pass for one reason or another before they make the internal pip. This is one reason when I set a hen or fill the incubator I add a few extra eggs then I technically want to hatch. I always try to give the broody girls at least 8 eggs hoping between non starters and those that quit at some point in the incubation process I will get at least 4 to 5 chicks. Sometimes it works and sometimes it does not. The last chicks Holly hatched I set her with the last 9 fertile Drumstick eggs, she had 2 hatch. 2 started to develop and stopped after a week, 1 exploded underneath her at 2 weeks in. She stepped on the first chick that tried to hatch and squished it. 3 more hatched out fine but passed within the first hour. Of the 2 that made it I got my keeper pullet Baby.