Q7FN 55" Green tint on screen

Hi Guys,

I have this issue with my screen displaying greenish gray from the center of the screen to bottom. I have searched everywhere but cannot find anything about this issue. I have contacted samsung and got the panel replaced 3 times, but the issue persist and exactly at the same spot. It is visible only on gray color especially on 5 - 10% gray level. I cannot see the issue with other color (most probably other color masked the green spot)

What is this issue called? What exactly happen, surely it is not a panel lottery ? as i have got the panel replaced 3 times with the same issue.

Any assistance would be appreciated. Thanks.