Tesla Motors Club

This has happened to me a few times, mostly recently early this morning --

Since I don't drive the car much I just use the 110v charger for normal charging. After running errands for the day the car usually has anywhere from a few to 10-20 hours of charging remaining when I plug it in.

This morning I heard a "buzzy" whine coming from the back of the car, presumably where the control box is. My app said the car was charging but still had 6 hrs to go. I didn't think to record the sound but I will try to remember next time ... but it specifically does not sound like the heat pump (which I believe is in the front of the car) ... it sounds more like an electrical transformer noise, almost exactly like this:
To reset this I basically used my app to "Stop Charging" and then "Start Charging", the noise stopped and the app (correctly) said 10 minutes left to charge.

I have not contacted Tesla Service about this one yet since it doesn't happen that often ... wanted to check with you guys first to see if anyone else has had this problem.

Thanks. John