I had an eerily similar experience during a flyover involving a freighter last summer. Preflight was fine, and I'd flown that same path over water several times before (including freighter flyovers) without incident. At 3:30 into the flight at 3300 feet out, 300 feet up, the signal went from good to fair, then back to good. I started flying her home at that point, when the signal and video suddenly disconnected a few seconds later and never reconnected for the rest of the flight. Her signal completely disappeared off the map. Thanks to God, RTH did engage, and she returned and landed safely but, that return flight home seemed like a whole lot longer than just a few minutes.