I don’t have any answers to this either. Some hens are put together differently genetically and they put their eggs together differently. Maybe this has something to do with it?
Early in a laying cycle, the egg whites are thicker than later in the laying cycle. Just before they are ready for a molt, the whites can be pretty runny. Is it somehow related to this?
Older hens can have problems putting the eggs together the right way, just like pullets can. But I don’t keep any hen past three years and I still occasionally have this problem so maybe this is not a cause. Maybe it could contribute for some hens? It could be a combination of things or separate causes.
Maybe how old they are or how warm they were stored? I open unhatched incubated eggs. With most of those it’s hard to open a totally undeveloped egg without breaking the yolk.
I don’t know what causes it either. Sometimes it’s a problem and sometimes it’s not.