Can you just add more hay? That’s what I use and don’t have that problem at all, but the lip on my nest is about 5” so I can add a lot of hay without them scratching it out of the way. Before a hen lays an egg she often scratches and rearranges the bedding to get it just the way she likes it. She makes a depression and raises sides around her making a nest. If there is not enough bedding she can reach all the way down to the wood.
Another potential cause if the same hen’s eggs are breaking is that her shells may not be very thick. If all the eggs are thin-shelled you have a flock problem and need to increase the calcium they are eating, probably by offering oyster shell on the side.
Some hens are much better at digesting the calcium they eat than others. Although they may be eating enough calcium it is not being digested and used for the egg shells like it should. That’s an individual hen problem, not a flock problem, and is probably genetic. Even if you are offering oyster shell or some other calcium supplement she may not have the instincts to eat as much as she needs. Most hens get that right but each is an individual. Not all have the right instincts or their bodies may not be just right.
Something else to check. Do you have nails, screws, or something else hard and pointy sticking up that the egg is hitting?