KD65X8509C - Slightly dark corners

[BrianDrought]

Hi, purchased this a week ago (yeah, I know). 

Anyway, on more solid coloured pictures such as a sky there are slightly dark patches in all four corners of the screen. About an inch square so not terrible, but slightly annoying. 

Being back lit as opposed to the 55" edge lit I was sort of assuming that there wouldn't be this vignetting issue.

On a complicated moving picture you can't really see them, but they do show up on block colours like kids animations. 

What I'm really asking.. does anyone else have a 65" 8509 and do you have slightly dark corners? 

Cheers,

     Brian (oh... the rest of it, including Android has been just fine....)

[Comicjoc]

Hi

i have also a recently purchased KD 65X8509c TV, 

I have not noticed the dark corners but have patch on screen & is very noticeable when watching a football match.

I have cleaned the screen will a damp cloth without much success & then tried with a spot of washing up liquid.

This has made a difference, but mark is still there.

Would love to try something stronger but too scared.

Anyone have any other ideas?