An update:
I took the car back to the dealership on Monday, for the second time to fix the fault with the aircon, because I went to a few Aircon specialists and they all said that "the electrostat is faulty and only BMW can replace it"
With both visits, the dealership did a diagnostics, it only detected the Cats missing and the rain/heater sensor by the rear view mirror. This sensor is what caused the aircon to not function properly. Replaced the sensor and the aircon is functioning properly
--------------------------------
The aircon was always set on 18C and auto fan speed. The problem that the aircon had was that it decided itself when to come on and switch off. Most of the time it didn’t switch on immediately when the cars ignition was switched on….. It wouldn’t switch off once the cabin got to the required temperature, it either turned off too early or it stayed on for too long, sometimes only going off when the ignition was turned off.
Sometimes I had to switch the aircon off manually because it got ice cold in the cabin. The one specialist put his temperature gauge by one of the dashboard vents, it read -3C and the condenser was icing up.
---------------------------------
The flat spot is still occurring
No one can figure it out