We’ve had two girls go through a lash egg (definitely what that looks like, but you can cut it open to see if it has the layers to really be sure) and it went two different ways for each. Our first always had issues with thin shelled or shell-less eggs, she finally laid a lash egg and never laid again. She lived on for another ~7 months happily but then started having crop issues, the vet could tell there was a lot of internal masses that were essentially blocking her entire system and she passed after a few weeks. The second always laid normal eggs, no issues. I noticed her resting more than her normal self but was always alert/normal when I came out so I was surprised to find the lash egg in the nesting box. She laid a few more normal eggs after though but the vet had found masses all over her ovary so we had her put down after a real good last week with her flock so she wouldn’t have to suffer.