session data lost after redirect in CI 3

I was facing the same issue and after a long research I found the solution.

My session is stored in db not in files but even database is also restricted to store the size, I think..

Its not any core issue of codeigniter or something that is session destroyed automatically or something else..

It is actually the load of data amount in session, if we save the more & more data inside session with Codeigniter("I am not sure about native session but for codeigniter I can confirm this"), it will destroy the session automatically.

So what you have to do is, to go to that code that you are writing to get the data from db or somewhere else and then saving into session in userdata, try to reduce the load of data saving inside the session and exclude that data which is not needed on page from session every time.

Let me know if still there is an issue..