While setting, hens turn the eggs, as they adjust their own position over the eggs. IS THERE A FRONT EDGE to your nest box, well above the nesting material (straw?) It is a myth that the hen will roll out an egg that is not developing. A hens instinct is to SET--and she waits until the eggs hatch. She cannot count the days--some hens will get off the nest if they do not hatch after a few more days after they are due, but some hens will stay for extra weeks! We have to look after their health, if this happens. If some do not hatch (I candle all eggs during the set, so I can remove any that are not fertile, or can see eggs that have red rings that show up, to indicate they stopped developing--so all are expected to hatch.) Most hens will take the chicks out of the nest a day or two after first chicks hatches (not all) and any eggs not hatched, are just left, because food and water for the chicks quickly becomes her next instinctive priority. Your eggs that are put back in the nest may be okay, but candling is the way to know. No way a hen could remove an egg from the nest boxes I use. I see pictures of many-- that I wonder how daily eggs don't roll out, much less those of a setting hen.
Actually, I use cardboard boxes for the nests. Select right sizes at the grocery store, close them up, cut a hole in the side (with good depth for the straw). Some have to be tacked to the wall, so they are not tipped over as the hens go in and out (or the rooster tips one, as he goes in to "check things out". I cut the door hole to the bottom, remove most of the straw, so chicks can use it, if the hen wants to keep them in the nest box for a while. Box, hen and her eggs she is incubating are moved from the pen, so she will not have another hen laying eggs in her nest!! THEN,when hatching is over, I cut the hole to the bottom of the box, so chicks can go in an out, if the hen wants to keep it for a haven. When she doesn't use it, you just toss it, and have a new clean box for the next laying session. No chance for mites to hide for the next use. If you get mites, it is hard to clean out the permanent nest boxes than look so neat. _Good luck!