Another player appears in the place I am before I click play in the editor

I’m newbie in Unreal Engine and I learning it programming Pong game with C++ (you can find my project in github).

This is the test I did.

In one position:


In another position:


And another position:


But If I comment the line that define the DefaultPawnClass = APaddle::StaticClass(); in GameModeBase:

	// Set the default pawn class used by players.
	//DefaultPawnClass = APaddle::StaticClass();

	// Set the class of GameState associated with this GameMode.
	GameStateClass = AMyPongGameStateBase::StaticClass();

	// HUD class this game uses.
	// We don't need to do anything else to use our HUD in the Game.
	HUDClass = AMyPongHUD::StaticClass();

The paddle doesn’t appear but instead of it, appears a ball:


First, this question belongs more to the
Now the real answer that you are looking for:
Most of the games, at a given level you want the player to control an actor that is given him right when the level starts, at it’s given place.
To make this process easier for the developers, Unreal Engine offers some tool.
When a Game Level starts, it automatically creates the given default character at a random “Player Start” actor, of it can’t find one, then at (0,0,0). That’s why you see this “bug”.
How to fix:
It’s not very hard to trick it so it won’t generate a bonus actor, but it’s much easier to use this function if it already exists.
Just set the Default Pawn to the pad of the Player 1, and put a PlayerStart actor where you want the player to start.
And delete from the level the pad that you put in manually.