Session issues

Sessions in a browser get other sessions by another users. For eg:

User A -> Browser Chrome -> IP 192.168.0.105
User B -> Browser Mozilla -> IP 192.168.0.200
...
User H...

If you sign in on User A and reflesh the page, automatically change to User C, or User H. Or any other users.

I'm using: php56, CI 311.

I already tried to save sessions on database and files, without different results.

Thanks.

PS: sorry for my english!