Re: Battlefield 4 "Reserving a slot" when i enter a server.

Well, usually when it happens (as I get it once in a while too), I do these things:

1) I choose "Disable Origin in-game" option in Origin settings (it solves quite many issues for some reason)
2) I log out of Battlelog
3) I make sure that bf4.exe isn't running (and if it is, I close the process in Task Manager)
4) I close Origin.exe process via Task Manager
5) Then I log back in to Battlelog, choose the server I want and join it. Origin launches itself, and game usually launches itself without an issue.