Since wiggling the display can affect the issue, it is possible the video cable is damaged. The cable runs thru the clutches in such a way as it can be pinched or wear thru the insulation.
The video cable is the blue and yellow cable running thru the right hinge in the following picture:
http://s2.guide-images.ifixit.com/igi/ioMWmfrpJRUfOATI.standard
This is a tough repair, as replacing the cable will require a complete teardown of the entire notebook and display assembly.