I think there is a T-con board hidden behind the black heat shield/covering in the Top middle section.
Could be T-con lvds or rvds problems though likely are the flexs, TCP problems.
its a reasonably good large TV, I would try to the very end.
So if it is convenient, swop a T-con.
I would probe the T-con, but it is too difficult and lengthy to explain here.
the simplest is to swop T-con board, press in all connection etc...