Screen partially black, which part should I focus to repair

Please see attached photo and video, which might give an idea for those who experienced similar situation.

The black area also shows ghosting, and without an impact, rarely it goes away by itself after some time of usage. I am using club 3d cac-1510a (non hdcp model) and the black region occurs also without the adapter (i.e. with a basic dvi to hdmi adapter).

Which card should I focus to replace or repair, what might be causing this issue? Any ideas would be more than welcome.

Let me try, thank you very much.