I'll get one like that with pullets sometimes whose body just hasn't matured completely and the reproductive system is still settling in. If that's an older chicken and it's consistent, I'd say a lack of calcium. If it's a one-off, I probably wouldn't worry about it.

Internet rabbit hole diver to the rescue:

https://www.chickenfans.com/soft-shell-eggs/

I can't 100% confirm the validity of all the statements in the above link but they seem to match the other things I've read.

#grownostr #ProfessionalAmateur #TrustButVerify

Hey if you are American I heard the "conspiracy theory" that some brands started putting weird stuff into their chickenfeed I would try to make my own chickenfood maybe that helps.

My farmer friend says fermenting their food will help. And don't use tractor supply feed, if you are.