This has happened a couple of times to me, and I think I've finally figured out the mitigation, so I thought I'd share for others who might experience it. My Model S is programmed to begin charging at 12:15 am to take advantage of TOU rates. A couple of times now, I've gone out to the car in the morning and it has not charged, and the only message on the screen was "Charging Stopped". The LED ring around the charge port was steady blue, indicating that power is available, but the car is not charging. If I unplug the charge handle and reengage it, the car will charge normally. I have an HPWC on a 60A breaker, with the HPWC is set to deliver 48A. The wiring on the charging circuit is sized appropriately, and when the car is charging at the full 48A, the car reports the voltage at 243-245V. Luckily, every time, I've had enough range for the day. The first time this happened, I took the car to the Service Center, and it happened there too. The SC pulled the logs, and the evaluation of the logs was inconclusive, but from past experience, they determined that the female pins on my charging handle had "loosened" and the pilot circuit connection between the HPWC and the car was intermittent. They sent out a crew and changed my HPWC cable for a new one. A few days later, it happened again - exact same symptoms and outcome. From my electrical engineering background, I agreed this looked for all the world like an intermittent connection. I procured some electrical contact cleaner, and with a cotton swab, cleaned out the charge port in the car, and the sockets in the charging handle. The cotton swab came out black, with gobs of grease and other foreign matter. The car charged normally the next few nights, but I had an appointment at the SC to investigate, so back I went. They pulled the logs again for the most recent incident, and determined that the on-board charger had lost the pilot signal as the charge session was beginning and had aborted the session. Under those circumstances, the charging session will not restart. The only way to restart it is to disconnect and reconnect. The SC technician agreed that cleaning the charge port pins had been the solution, but they proactively installed a new charge port. Moral of the story, keep the connections clean! This will now be part of my wash routine every month or so. There are several good electrical contact cleaners available which leave no residue but will help remove any impediment to a good electrical connection.