So, since I've had my heat pump compressor and sensors replaced, I've had a burning smell for the first 30s-1m of it running in colder weather, usually right when I start the car for a drive. I have a Tesla Mobile appointment scheduled for tomorrow and will let you know what they find, but wanted to see if any other heat pump owners have had this issue. Issue didn't exist when I first got the car; it showed up after they did the repairs.