Lg 60lb6100UG - Left side of screen is dark, but backlight LEDs work

The left side of my Lg 60lb6100UG is dark, slowly taking over the right side. I opened the TV believing some of the left side LED strips were out, but the entire array tested bright and functional. Could it be the T-Con board or the backlight inverter on the power board or a bad ribbon/cable? Any suggestions would be awesome!