You have a special situation. You have a history of them having this problem. If it were just one hen I'd suggest she is either not eating the extra calcium you make available or her body is not processing the calcium she does eat. You are dealing with living animals. While most might a body that reacts as it should or most will have certain behaviors, not all do. If she were the only one I'd suggest you have an individual hen problem, not a flockwide problem, and you should treat the individual and not the rest of the flock.
It sounds like she was laying a no-shell egg. Do you often get no-shell or soft shelled eggs? It sounds like you might. Or double yolked eggs? That could indicate another issue.
Some people feel you need to feed them a high amount of protein. They have their reasons for that. I don't, partly because they survived and thrived for thousands of years by getting everything they eat by free ranging, humans not feeding them anything. To me the increased protein is more about production, not health. But many people I respect on here consider the higher protein necessary.
I don't know what is going on. Since what you are doing is not working I'd switch to the other feed. I don't know if it will help or not but it is something you can easily change. I would continue to offer the oyster shells free choice.
You can cut back or eliminate those fruits and veggies too. Those should not be causing any problems unless you feed them a lot but they are not necessary. Your feed contains all that your chickens need, they don't need anything from those fruits or veggies. People feed them because it makes them feel better because they think they are helping or they are making the chickens happy. I feed mine fruits and veggies in season, but mine forage for a lot of what they eat anyway. I don't try to micromanage every bite they eat.
Good luck. I do not consider your problem as something easy.