I have been using broody banty hens this year and have had excellent success with them being able to set up until about 3 days before hatching, then i pull the eggs and set them in the hatcher, i only had one egg that didnt hatch out. I really dont think its a moisture issue, i just watched my mandarin hen come out of the box this morning and get some food and something to drink, while she was out i peeked in the box and the eggs are pipped, so i left and she didnt bathe at all, just went back into the box and set on her eggs again.
There is definitley something majical about natural mothers, something humans rarely duplicate.
Sorry to hear about your loss, its heart breaking when you spend the time and money for a month caring for the eggs only to have them die or hatch and then die. But, its trial and error, and you did the best you can!!..............Jason