In 2.4A load the output voltage drops slowly and after 50 minutes at less than 4.7V. This is too little, showing that the device is overloaded. When the voltage at 5.1V 2.1A remains, making it perfectly fine. Here perhaps someone has the capacity of a unit 2A by "umlabeln" increased. After all, it is not too hot even with 2.4A.