it would help me tremendously if you could tell me your GPU, especially since you also said you don't think it's a CPU issue. i have an office grade laptop with an integrated graphics card, and i get steady 60FPS, so it could well be a GPU/driver quirk or Godot simply choosing the wrong GPU on your system. if you are on windows, there is a %APPDATA%\Godot\app_userdata\Kraft\logs\godot.log file which says what GPU the game selected on startup.