1) put a 1920x1080 grey picture (grey picture = uniform grey everywhere, create it with your computer) on a USB key and plug it on the TV. The picture must not be white, it must be a dark colour.
2) visualize this picture with the TV, from a distance, eg. 3-4 ft
3) now look very closely at the exact center-top of the panel. You should see two tiny vertical lines/strokes about 1 inch apart from each other.
Do you see them? I would bet these things have something to do with the uniformity issues (if any)
I have a 42 inch TV. Not sure if this can be seen with other TV sizes.

