&1 was called to update session &2. The update was not done as user &3 is already logged in.
&1 - The name of the function that attempted to update the session
&2 - The session id
&3 - The user that is registered for the session
The function specified in the function attempted to update the session with user information. This attempt failed as a user is already registered for the session. It is not allowed to change the user for a session - or remove a user that is already registered for the session.
Check the calls to the specified function. For each call, ensure that the session has no user registered.