alinas2010, I just realized I am having this same issue too. I have a small flock of 6 red sexlink Isa Brown hens (high egg production girls) and 1 Brahma roo. The girls were all hatched ~Sept 1, 2022 (not quite 1 yr yet); I got them from a farm in Jan of this year before they started laying. They get to free range a few hours a day (we're still a little hesitant since we lost our previous flock to a hawk attack back in Dec).
Anyhow, about once every 2 weeks, one of my girls, Amber, starts getting a bit weird and she goes off into the corner of the run by herself and stands there with her vent opens, typically it happens later in the afternoon like around 4 or 5 pm. On some occasions she starts secreting parts of an unformed egg, and then later in the night from the roosting bar she'll drop a partial egg where the shell didn't form properly, and then like last night, next to that partial is a soft egg where the shell formed a bit, but not completely, enough to land in the bedding below and have some integrity. On other days, she'll drop 2 bad eggs with just the "wrapper" of a shell in the nesting boxes. And then when she's back to regular laying, maybe a day or 2 later, the eggs slowly come back to looking normal, but are thin shelled for a day or so.
I'm wondering if Amber has cancer because her behavior is similar to one of my girls that had cancer last year?!?
alinas2010, one of my theories on the thin shells is that these girls are eating enough calcium for one egg to form, but not for 2 to form, and thus their bodies are trying to split the calcium between the 2 eggs instead of using the calcium to form one good egg. I've injected a little extra calcium into Amber to see if that helps, but what I haven't figured out is how to stop her little body from producing 2 eggs??? That's the root of the issue, but the fact that the shells are thin is a result of the issue. If anyone has any thoughts on this issue, rather than the shell issue, I'm curious as to how to stop this. Websites say, yes it can occur, but they don't give insights on how to fix the issue.