Did you make the call? If new, did you squawk loudly?
https://www.google.com/search?q=55UF850T&ie=utf-8&oe=utf-8#q=55UF850T+local+dimming does find it has local dimming and many of these smart TVs have firmware updates to correct issues like this. Call it in fast.
I am using Lg55UF850T. Randomly whenever I am some movie or playing some games (PS3) THE FOLLOWING THING HAPPENS. Picture attached. https ://flic.kr/p/ EtfUSF
TO explain further....The complete black does not appear suddenly.It starts from the left and right edges and slowly occupies the fullscreen.
But when I turn the TV off and then ON everything is back to normal. This is happening randomly. Also for few videos it starts to happen immediately and for some videos it takes some time. I dont know what this is,and its driving me crazy....
please please please help

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