As @SteveRambo said, its better to have an empty level as your “MainMenu” level, and transition to the default level from there using your current logic.
The problem currently is that you’re creating the widget and adding it to viewport on the default level (ThirdPersonMap) and then loading that level again, which causes the widget to be re-created and added to viewport, thus not working as you want it.
If you do not want to create a new level, you can just call “Remove from parent” after all the logic on the start button (“Button_280”).
Also I highly recommend you name your buttons on widgets so you do not get confused later on.