I've got an Olimpia Splendid Ellisse HP portable heat pump with strange/incorrect thermostat readings. According to another thermometer the room temperature is currently 16.9C, the heat pump thermostat reads 22C, that is a significant 5C difference. That means to warm the room to 21-22C the heat pump must be set to 27-28C. When I set the heat pump to 27C (max) it will only run for a few minutes before it thinks it has heated the room to 27C. What's wrong with this thing? It is a brand new unit.