Lower half of screen goes dark.

Model is panasonic tc-l58e60

See pictures of the problem. I was told by the only TV repair shop near me over the phone that the panel is possibly gone bad. If I leave the TV unplugged for a couple days the display is 100% clear and works fine for about 2 hours before the lower half goes dark and fades left to right. I replaced the main “A” board as that’s what someone had mentioned it could be. Didn’t fix the issue. Should I try the “P” board next? I just don’t I understand how the screen can work fine and be so crystal clear and then just half of the screen crap out like this.