Chosen Solution
My brand new TCL set had these lines randomly appear while I was watching a movie. What could be the problem?
That looks like a bad Panel. Possibly the TAB connections from the LCD driver board. You can check it by removing the back from your TV and look for a thin ribbon cable that enters the panel. Apply pressure on it and see if that lines disappears. If so it’s a TAB error. Since it is a new TV I would return it under warranty
