Cracking a boiled egg shouldn't be this hard

I thought I mastered the art of boiling an egg once I had learnt that once the water is boiled drop the eggs in and cook for 9 minutes. The yolk was perfectly solid but still yellow in color. I seem to cook eggs on a regular basis and every blue moon or so I notice the batch of eggs are extremely hard to de-shell (not even sure that is the proper term). Why does this happen? It's not an organic versus conventional thing because it has happened with both kinds. It isn't a brown or white shell thing because that has happened with both as well. Is it the small egg versus the large egg? I never tested that theory out. I don't know. All I know that some batches that I buy are extremely hard to de-shell. So much of the white part of the egg won't detach from the shell. And in those circumstances the egg cracks in so many little pieces that i just just all of it in the garbage because it is too much work to save. Once in a while I have a breakthrough (excuse the pun) and slowly save a lot of the egg but can't seem to remove that transparent lining that makes the egg taste not so grand. Is this an egg past their expiry? Is their a procedure with boiling eggs that I am not familiar with? My large boiled eggs became rather small and disfigured once I de-shelled. If you know of any tips, please pass on. Share your story.