Triangular Eggs

Cleopatra is no "SQUARE" - she's very "HIPP" because she lays triangular shaped eggs! When I go out to collect the eggs, I've been noticing that one egg (a blue egg - ALWAYS a BLUE egg) has a flat side! Then a few weeks ago, the flat sided egg has had a hole in it. Hmmmmm. At first I thought someone had pecked that hole. But, every hole is the same size, about the same shape, and always it's that blue flat sided egg!
Couldn't figure out which hen was the culprit. There are 2 of them that lay blue eggs. But finally I caught Cleopatra in 'the act'! I opened the nest box lid, and there she was, straining to get that egg out...ONE....TWO....THREE.....FOUR.....FIVE! And out it came! She left the nest box, and I picked up the egg, hot from the hen. I examined it, and this is what I found - - -This egg is triangular! Can you see the gently formed curves?? But oddly enough, there was no hole in the egg. I brought it into the house and set it on the towel, as you will note in this picture. After about a minute of sitting there, POOF! The hole appeared!!! It was like the pressure was equalized as the egg cooled to room temperature, and it sucked that portion of the shell inside the egg, leaving a crater! Ever seen anything like this? I'm wondering what caused it and how we can fix the situation! Stay tuned - if I figure it out, I'll certainly fill you all in on it!

Have a great weekend -