I have a 75" QLED TV that displays both a vertical black and vertical gray bar in the center of the screen. The bars are solid. The bars look like a bar graph. The bars are each about 2 inches in width. I have replaced the power supply board that fixed a couple of grayish vertical shadows. I have replaced the main board. I have replaced the FCC ribbon cables. I've cleaned the connectors and reseated them. Any other ideas to fix this would be appreciated. Thanks.