I have some trouble hatching duckings. I live in semi desert, our starting humidity is about 25% and it's a bear getting it over 50%. Now, if I were just patient in the spring, my Saxonys go broody on the 1st of May like clockwork. Pumpkin hatched 10 of 12 eggs this year!
My duckings tend to be a slow hatch (probably the dryness, I even run a humidifier in the room with the incubator!) and I'm used to a day or more from first pip to the duckling, though they can be faster. They will hatch late for me too, I think my incubator tends to run cool.
This year was tough with the incubator - I ran it for three weeks, then checked the temperature with a new thermometer and realized I was running my still air at 103!! I turned it down, found I still had four wigglers from the outside corners... then the power company called and said they were going to turn off our power to work on the lines. I had the power out for 5 hours - put in hot water bottles and hoped. I hatched one of those eggs. I had Anconas sharing a nest for 5 weeks about this time... I pulled them off their eggs. Turned out they'd gotten 34 eggs in a little dog house and several of them were still alive on candling. I put them in the incubator and managed to hatch 4 of them - six weeks after the girls started sitting! I guess they kept laying, as they didn't have anywhere near 34 eggs when they started. I won't let those two do that again! Next time the Saxony can do the work. I've two wonderful experienced Saxony mothers, they can each have a nest and hatch anything I need hatched on any given year and they won't be 103 or turn the power off!