Do you know when those eggs were eaten? Was it one at a time or all at once? Day or night? What do the broken eggshells look like? In tiny pieces or more in halves? Are all the inside egg parts gone or is it a wet mess? Are the eggshells in the nest or in the area? Can you put a game camera out there to see if you can film something?
After 7 days 5 eggs are gone with eggshells left behind. Frankly that sounds weird. Whatever is going on I would have expected it to be all or none by now.
If it is your hen eating them there is nothing you can do about it other than putting the remaining eggs in an incubator and hatching them yourself.
It could be some other critter. Since the eggshells are left it is not a snake. I've had a snake eat eggs out from under a broody before. Kind of creepy but no eggshells were left behind. A possum or skunk could eat some eggs and leave some I guess, but I'd expect them to eat them all unless they were scared away. And I'd expect the shells to be outside of the nest. It could be a rat. I don't know where in the world you are located, you may have other local egg eating predators.
This is a strange one to me. Good luck figuring it out.