Toggle.isOn= var calls StackOverflowException+ Logs

      [SerializeField] private Toggle fullscreenToggle; //selected in inspector
      private bool doShowFullscreen;
      public void Start()
      {
          doShowFullscreen = (PlayerPrefs.GetInt("doShowFullscreen") == 0);
  
          fullscreenToggle.isOn = false; //ok
          fullscreenToggle.isOn = true; //ok
          fullscreenToggle.isOn = doShowFullscreen; //StackOverflowException
      }

Logs:

[MODES] Loading mode Default (0) for mode-current-id-Pirates: Mystery of Skeleton Island Mono: successfully reloaded assembly - Completed reload, in 1.728 seconds Platform modules already initialized, skipping