I suspect you all are experiencing a feature, not a fault. When the i3 launched, I recall BMW's press materials calling out the automatic bi-level climate control. Once the set temperature is reached, the system routes cool air to the dash vents and warm to the floor. The idea being that cooler air in your face keeps you alert while your feet stay warm. If you precondition, the cabin will be at your set temperature when you start off so it's logical that the automatic bi-level feature would come into play immediately. Personally I don't bother with preconditioning since I drive such short distances. I have noted that when temperatures are colder, I get warm air from the dash vents initially then the system will switch to cool. If you don't like the effect, you can switch to manual and force the system to send air only to the floor vents.