A flashing display indicates that the heating element is disengaged and the kettle is not heating (i.e. the kettle is "idling"). This happens when the hold switch is turned off, the kettle reaches the selected target temperature and, either,
1. The kettle sits for 5 minutes
2. The kettle is removed from the base.
If you'd like the kettle to return to the target temperature when you place it back on the base or maintain the target temperature for more than 5 minutes, turn the hold switch on. Otherwise, when the screen flashes, the target temperature must be re-selected while the kettle is not seated on the base.
With hold function enabled, the Stagg EKG maintains the target temperature for 60 minutes. When the kettle is removed and placed back on the base, it will register a drop in temperature and begin to re-heat to the the target temperature. After 60 minutes, the heating element disengages and the kettle will idle for 15 minutes before turning off (i.e. the screen shuts off).