Pretty sure my hatcher is faulty as it's saying 37.7 but it feels far to hot in there! I got the duckling out as all the others have died I put it in a little tub with a cloth in it and in the brooder with my other two which to my surprise 5 minutes of it being in there and it's bounced right back up!! My chicks can't reach it they aren't fussed anyway but I think the noise of them is giving the little duckling a push. First noise I've heard from it and the yolk has reduced quite abit! Fingers and toes crossed
Definitely get an independent thermometer, test it for accuracy and double check it against the unit.
Did the yolk break, or was it just not all absorbed when it hatched? Usually they can absorb it pretty quick, but if it actually ruptured, you need to make sure that little one starts eating (and pooping) quickly. Without the yolk absorption, it will need it.