I had ghost touch issues on my x1 tablet, and it very much looked like a hardware issue - so I replaced the screen. Great. But 4 weeks later the screen suddenly lost all touch and pen functionality. After quite a bit of fiddling around I found the culprit - it is the "touch controller card cable". See page 68 of the hardware maintenance manual - section 1080.
The cable connects in the middle of the laptop and to the right bottom side. And its the right bottom side where the cable was not quite fitting into the socket. Reason: the cable was glued about a mm to far to the left. Solution: I warmed up the cable using an ice/hot pack, and also a knife like tool from ifixt. Using said tool I could slowly, carefully loosen the cable from the underlying surface, and move it a bit to the right.
Now the socket closes nicely, and the screen works completely fine again!