My guess would be crushed cable, but your symptoms could indicate either the cable or the inverter. I lean towards the cable because touching or moving the machine has an effect. Tapping up and down on the brightness does nothing other than cause the damaged cable to temporarily connect.
Check with iFixit to see if they have a replacement cable. This is quite a repair to do yourself, though, since you'll likely have to disassembly both the bottom and top case to thread the cable through the hinge to the panel.