I'd get repair estimates as the backlight looks to be in the panel. A tech could try a few things before committing to a panel.
My Samsung LED TV Model : UN55D8000YFXZA the screen 3/4 of the screen is not normal only 1/4 at the bottom is normal
I need to wait for 10-15 minutes for this to become normal or turn on and off a few times.
I would like to know anyone had the same problem and how to fix it.