Why is an extra player object spawning?

Yes, that could be related with how you spawn your player manually. GameMode handles spawning of PlayerControllers and Pawns automatically, if you didn’t change it.

I am not sure if this a BP or C++ project, so I can’t really say much more, but here is the a useful documentation article about GameMode that you should read.

Also this one

Not sure what kind of game you are making, but it is usually best to stay within Unreals framework. So I would advice to set up a proper GameMode and let it handle the spawning of PlayerPawn and Controller.