I also suspect that they are laying out in the "wild" as you say. When mine free-ranged occasionally I would have to lock them in for a while to make sure they were laying in their nest boxes, this also forced them to eat more layer for a couple of days with the "correct" amounts of protein and calcium supplement.
If they are REALLY laying that many shell-less eggs, maybe calcium is a big problem for them. I never had very many shell problems when free-ranging though, grass and bug "shells" have calcium in them
The only one of my girls that lays shell-less eggs from the roost with any frequency is getting up in age, so I'm pretty sure age is her problem.
I notice that as the oyster shell sets out in the weather (Arkansas humidity) it will set up like poorly mixed concrete. They don't seem to eat much of it when it's like that. I put out fresh and they come over and eat some right then. How are you feeding it and are you keeping it fresh-ish?
If they are REALLY laying that many shell-less eggs, maybe calcium is a big problem for them. I never had very many shell problems when free-ranging though, grass and bug "shells" have calcium in them

The only one of my girls that lays shell-less eggs from the roost with any frequency is getting up in age, so I'm pretty sure age is her problem.
I notice that as the oyster shell sets out in the weather (Arkansas humidity) it will set up like poorly mixed concrete. They don't seem to eat much of it when it's like that. I put out fresh and they come over and eat some right then. How are you feeding it and are you keeping it fresh-ish?