I agree that it is the screws inside the back panel. Mainly the ones holding the LED module. How would they know its been unscrewed and opened up? I see no stickers or anything.
Also I have had literally 6 sets. First three had a dead pixel that was viewable in anything. Also had edge bleeding and some banding/dse but by far the best out of other tvs i have tried.
The next three sets all looked the same so I stuck with the one that i have been using since it has not had any 3d problems/ restart problems/ dead pixels. Only edge bottom corner bleeing and minor banding/dse.
I think danediz has gotten lucky and I envy you.
I have had March, Nov, Nov, Sept, Sept, Sept manuf date and surprisingly the March is the best for me