The person who suggested a wi-fi conflict was right on. We recently had a power outage due to a thunderstorm and the surge completely reset my tp-link router. We finally realized that the problem appeared after the outage. We have ROKU and do not use the smart tv features of the tv, so I disconnected it completely from the network and did a factory reset and, voila, the problem is gone. Everything is back to normal. Hallelujah!