T430 backlight problem

[T-Opel]

Hello, I have a T430 and for the past month I have been having some issues with screen backlight on the laptop. At the bottom part of the screen there is a spot that is not backlighted. But this problem only happens sometimes, it usually disappears when I connect a second monitor or restart the computer, so it does not seem to be a hardware problem. It seems to be entirely random, but it keeps getting "worse", now I have to reconnect the second monitor 10+ times for the problem to disappear.
http://i68.tinypic.com/fw0gsi.jpg
Do you have any idea what could be causing this? I have Windows 10.

Thx

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