If this is their first clutch of eggs, poor incubation techniques are very common. Let them keep practicing on this clutch and when she loses interest in the eggs, discards them or eats them, then go ahead and take the box down for a few weeks so they can have a short rest, and then let them try again. Of course if the eggs end up hatching, that is great! When they have hatched and raised chicks, the nest box should be removed once the chicks have left it, and the parents should be rested for a few months. It’s best for their health and for healthier chicks if you limit them to about 2 clutches in a year. In the wild they would generally only have one clutch per year. In captivity they will keep breeding all year, so it is up to you to force them to take a break.
If this clutch does fail, and they fail on the second clutch, give them about a 6 month rest before you let them try again. They are inexperienced and if you let them keep trying and failing, they can develop bad habits and will never be good breeders. They might need to get a bit older before they settle down and take care of the eggs. And some birds will never make good breeders. When a pair continues to fail with clutches, it is best to stop giving them a nest box at all and no longer try to breed them.
Thank you for asking Lafeber,