We have seen an issue with the heating system twice here in the NY/NJ/CT area. Once my wife was in the car and we had the heat set to 19.5C which was fine but after running for awhile the air coming out of the system felt cool instead of warm. My wife who is not a fan of the cold noticed at first and the solution was to turn up the heated seats. The second time I was doing a drive by myself to Philadelphia to visit family and again instead of warm air coming out of the system it felt cool. I just turned off the fans and put on a pair of gloves I had in my coat pocket. I do warm up the car for about 20 minutes before starting a drive via the app (Climate > Defrost) and so far every time we get in the car is warm so it is not like the system is completely broken. I haven't followed up with Tesla because getting a time slot at the nearest service center has not been easy.