Most low and Mid end 2014 LG television use the direct LED backlight system. This system has been greatly improved over the 2013 versions. They are thinner and offer better quality.
The direct LED system works with LED's directly behind the television screen. However this system is not able to project the same amount of light into the corners as to the middle of the screen. Although this is a slight difference, the corners will appear darker in light scenes, or light backgrounds. This is not a defect in the panel, this is inherent in the technology and can not be fixed by a repairman, or be solved by exchanging the television.
Using lower backlight or brightness settings might reduce the problem.