Weird umbilical cord attached to egg??

[Peggysaurus]

Hey everyone! Recently, my dad found an egg from one of the nesting boxes that had a weird umbilical-like cord attached to the end of it (I'm just going to say umbilical cord because that's the best way to describe it). The point where the umbilical cord thing attached to the egg was very soft. It appeared to be part of the egg. I cracked the egg open and everything looked normal. I never had this happen before. Did the hen in question push too hard to get the egg out? Will she be able to lay again?

 

[Wyorp Rock]

It's an egg with a tail.
Egg was probably sitting in the shell gland for a period of time. If it's a one time thing, then likely a glitch.
https://www.yellowbirchhobbyfarm.com/weird-eggs-101-the-oddities-explained/